How to Make a Homemade Peanut Butter Layer Cake That Bakes Up Moist and Frosts Smoothly

Essential Concepts

• Use a stable, creamy peanut butter to avoid oil separation that can throw off texture and moisture.
• Combine butter and neutral oil for flavor plus tenderness, since oil stays fluid when cool.
• Buttermilk adds acidity and moisture, helping the crumb stay soft without tasting tangy.
• Stop mixing as soon as the flour disappears to prevent a tight, dry cake.
• Keep the finished cake covered and refrigerate within 24 hours because the frosting includes cream.

Peanut butter layer cake is a classic American-style cake built around two ideas: a tender crumb that stays moist for days, and a frosting that tastes clearly of peanut butter without becoming heavy or greasy. In practice, peanut butter can make cakes tricky. It contributes fat and solids, and it can vary widely from jar to jar. Those variables affect mixing, rise, and the final mouthfeel.

This article gives the “know simple” answers first, then moves into the “know” details that help you control the result. You will learn what to look for in peanut butter, why this batter uses both butter and oil, how buttermilk and leaveners shape the crumb, and how to troubleshoot common problems like a dense center or a frosting that feels grainy. A complete recipe in U.S. and metric measures is included, along with practical storage guidance and options for adjusting pan size.

What makes a peanut butter layer cake “moist,” and why do some turn out dry?

A peanut butter layer cake stays moist when the crumb holds water well and the fat stays evenly dispersed. Dry peanut butter cakes usually fail for one of three reasons: too much flour, too much mixing after flour is added, or a peanut butter choice that behaves unpredictably in batter.

Moisture in cake is not only “wetness.” It is the sensation of softness and lubrication when you chew. Sugar binds water, fat coats starch and proteins, and acids can keep the crumb tender by limiting excess gluten development. Peanut butter complicates this because it adds fat and fine solids that can thicken batter and make it seem “done” mixing before it truly is.

If you want a reliably moist cake:

• Measure flour carefully, and do not pack it into the cup. A scale is more consistent.
• Keep mixing gentle once flour enters the bowl.
• Use room-temperature ingredients so the batter emulsifies instead of breaking.

What kind of peanut butter works best for baking a layer cake?

For a predictable layer cake, choose a creamy peanut butter with a stable, uniform texture. In plain terms, you want one that does not have a thick layer of oil floating on top that must be stirred back in every time.

Peanut butters that separate can still work, but they introduce a measuring problem. If you scoop from the top, you may add too much oil and not enough peanut solids. If you scoop from the bottom, you may do the opposite. Either way, the cake’s tenderness and rise can shift.

Creamy vs. crunchy

Use creamy peanut butter for the batter and frosting if you want a smooth crumb and a frosting that spreads cleanly. Crunchy peanut butter can be used, but the pieces can drag through the cake’s crumb and the frosting, making a rougher slice.

Sweetened vs. unsweetened

Both can work. Sweetened peanut butter may push the cake and frosting slightly sweeter, and the effect can be noticeable because peanut butter is used in both components. If your peanut butter is sweetened and you prefer a less sweet cake, you can reduce the granulated sugar modestly, but avoid large reductions. Sugar affects tenderness, browning, and moisture retention, not only sweetness.

Salt level

Salt varies widely. If your peanut butter is noticeably salty, keep the salt in the batter at the lower end and adjust the frosting salt to taste. Salt should sharpen flavor, not announce itself.

Why do this cake and frosting use specific ingredients?

This cake is built on a common American mixing approach: creaming fats and sugars, then adding eggs, then alternating liquids and dry ingredients. The ingredient choices support that structure.

Cake flour blend and cornstarch

All-purpose flour provides structure. A small amount of cornstarch softens the crumb by reducing the flour’s effective protein concentration. Cornstarch also helps absorb moisture and can make the slice feel more delicate.

Baking powder and baking soda

Baking powder provides lift through a chemical reaction that produces carbon dioxide in the oven. Baking soda needs acidity to react effectively. Buttermilk supplies that acidity, which improves rise and browning and keeps the crumb from tasting flat.

Butter plus neutral oil

Butter contributes flavor and a fine crumb when creamed with sugar. Neutral oil contributes tenderness because it stays liquid at room temperature and even when the cake is chilled. That matters for a peanut butter cake, which can otherwise firm up as it cools.

Brown sugar plus granulated sugar

Brown sugar contains molasses, which holds moisture and adds a mild caramel note. Granulated sugar supports lift and a clean sweetness. Together they help the cake stay soft without tasting heavy.

Buttermilk

Buttermilk adds moisture and acidity. If you do not keep buttermilk on hand, you can approximate it (details below), but real cultured buttermilk tends to give the most consistent texture.

Homemade Peanut Butter Layer Cake Recipe (U.S. and Metric)

Yield, pan size, and timing

This recipe makes one two-layer 8-inch cake (about 12 slices, depending on how you cut it).

• Oven temperature: 350°F (180°C)
• If using convection: reduce to about 320°F (160°C), but convection varies by oven
• Pan size: two 8-inch round cake pans
• Bake time: about 30 to 35 minutes
• Cooling time before frosting: at least 1 hour, often longer

Ingredient notes that affect outcomes

• Room temperature matters. Cold butter and cold dairy do not blend smoothly, which can lead to a heavy crumb or uneven rise.
• A kitchen scale improves consistency, especially for peanut butter and flour.
• Use a neutral oil (such as a mild vegetable oil). Strongly flavored oils can distract from the peanut butter.

Ingredients (Cake)

Ingredient	U.S. measure	Metric
All-purpose flour	1⅔ cups	210 g
Cornstarch	3 Tbsp	24 g
Baking powder	2 tsp	8 g (approx.)
Baking soda	½ tsp	2 to 3 g (approx.)
Fine salt	½ tsp	3 g (approx.)
Unsalted butter, room temperature	⅓ cup	80 g
Neutral oil	⅓ cup	75 g
Granulated sugar	½ cup	100 g
Light brown sugar, packed	¾ cup	150 g
Creamy peanut butter	⅔ cup	150 g
Large eggs, room temperature	3	3
Vanilla extract	1½ tsp	7 to 8 g (approx.)
Buttermilk, room temperature	1 cup	225 g

Ingredients (Peanut Butter Frosting)

Ingredient	U.S. measure	Metric
Unsalted butter, room temperature	1½ cups	340 g
Powdered sugar	3 cups	375 g
Vanilla extract	2 tsp	10 g (approx.)
Heavy cream or whipping cream, room temperature	½ cup	120 g
Fine salt	½ tsp	3 g (approx.)
Creamy peanut butter	1 cup	250 g

Step-by-step instructions (Cake)

1) How do you prepare the pans so the layers release cleanly?

Grease two 8-inch round pans and line the bottoms with parchment circles. This reduces sticking and helps the layers unmold without tearing.

If you skip parchment, release depends heavily on pan material, how evenly you greased, and how long the cake cools in the pan.

2) How do you mix the dry ingredients evenly?

In a bowl, whisk together the flour, cornstarch, baking powder, baking soda, and salt until uniform. This spreads the leaveners so the cake rises evenly.

Sifting is optional, but it helps if your flour or cornstarch is lumpy.

3) What is “creaming,” and how long should you do it here?

Creaming means beating fat and sugar together until the mixture is lighter in color and texture. Here, beat the butter, oil, granulated sugar, brown sugar, and peanut butter on medium speed for about 3 minutes, until the mixture looks smoother and slightly aerated.

This step builds early structure. If you under-cream, the cake can bake up heavier. If you over-cream in a very warm kitchen, the mixture can become too soft, which reduces lift.

4) How do you add eggs without breaking the batter?

Add the eggs one at a time on low speed, mixing briefly after each. The batter should look cohesive, not curdled.

If it looks separated, your ingredients were likely too cold or the fat phase was too warm. Continue mixing gently; it often comes back together once the buttermilk is added, but a badly broken mixture can still bake unevenly.

5) When do you add buttermilk, and why does it matter?

Add the vanilla, then pour in the buttermilk and mix on medium speed just until smooth. Buttermilk hydrates the batter and supplies acidity that supports the leaveners.

Do not mix for long once the batter is smooth. Excess mixing at this stage can reduce tenderness.

6) How do you add flour without making the cake tough?

Add the dry ingredients and fold by hand with a spatula until no dry streaks remain. Folding means turning the batter over itself gently, rather than beating it.

Stop as soon as the flour disappears. Overmixing develops gluten, which can make the cake chewy and dry.

7) How full should the pans be, and how do you bake evenly?

Divide the batter evenly between the pans. Tap each pan lightly on the counter once or twice to release large air bubbles.

Bake for 30 to 35 minutes, or until a toothpick inserted in the center comes out clean or with a few moist crumbs. If the toothpick shows wet batter, keep baking and recheck in a few minutes. Oven performance varies, so rely on doneness cues more than the clock.

8) How long should the layers cool before frosting?

Cool the cakes in the pans for about 15 to 20 minutes, then turn out onto a rack to cool completely. Frosting warm cake can melt the butter in the frosting, leading to sliding layers and a greasy finish.

If your kitchen is warm, you can chill the layers briefly once they are room temperature. Do not wrap them while they are still warm, or you will trap steam and soften the crust.

Step-by-step instructions (Peanut Butter Frosting)

1) What style of frosting is this?

This is a peanut butter buttercream, meaning butter is the primary fat and powdered sugar provides sweetness and structure. Cream and peanut butter affect texture and flavor.

2) How do you keep it smooth instead of grainy?

In a large bowl, combine the butter, powdered sugar, vanilla, cream, peanut butter, and salt. Mix on the lowest speed until the sugar is moistened, then increase to medium-high and beat for about 8 to 10 minutes, scraping the bowl halfway through.

Longer mixing helps dissolve sugar clumps, smooth the texture, and incorporate air for a lighter spread. If it still feels grainy, your powdered sugar may be lumpy. Sifting can help.

3) How do you fix frosting that is too firm or full of air bubbles?

If the frosting is too firm and looks pitted, ingredients were likely too cool or the mixture whipped before it softened. Warm the frosting gently, a few seconds at a time, stirring between bursts, just until it loosens. Then rewhip briefly.

Be cautious with heat. Melted butter will turn the frosting loose and shiny, and it may not re-emulsify cleanly.

How do you assemble and frost a peanut butter layer cake so it slices neatly?

A neat slice comes from flat layers, a stable filling thickness, and a short chill before serving.

Leveling the layers

Trim domed tops so the layers sit flat. Use a long serrated knife and keep the blade level. If the layers are very soft, chill them for 20 to 30 minutes first.

Filling and stacking

Place one layer on a plate or stand. Spread an even layer of frosting on top. Set the second layer on top, cut side down if you leveled it, which helps keep crumbs contained.

If you want extra insurance against sliding, chill the filled cake for 15 to 20 minutes before frosting the outside.

Do you need a crumb coat?

A crumb coat is a thin first layer of frosting that traps loose crumbs. It is optional, but helpful if your cake is very tender or you plan a smooth finish.

To crumb coat, spread a thin layer over the whole cake, then chill until the surface feels set, usually 15 to 30 minutes depending on refrigerator temperature. Then apply the final coat.

Final frosting thickness

A thicker coat looks cleaner and protects the crumb from drying. A thinner coat uses less frosting but can show more crumbs and unevenness. Choose based on preference and how much frosting you prepared.

What are the most common mistakes with homemade peanut butter layer cake?

Why did my cake turn out dense?

Dense cake is usually caused by overmixing after flour is added, expired leaveners, or ingredients that were too cold to emulsify properly. It can also happen if flour was overmeasured.

Quick checks:

• Make sure baking powder and baking soda are fresh.
• Mix gently once flour is in the bowl.
• Let eggs and dairy warm to room temperature.

Why did the center sink?

A sunken center typically means the cake was underbaked, the oven temperature was too low, or the batter was overaerated and then collapsed. Opening the oven early can also contribute.

Bake until the center is set and a toothpick shows only crumbs, not wet batter. If your oven runs cool, you may need extra time.

Why does the cake feel dry the next day?

Dryness usually comes from exposure to air or too much flour. A cake that is not covered will stale quickly, even if it was moist when fresh.

Once frosted, store the cake in an airtight container. If unfrosted, wrap layers tightly. And avoid refrigerating unwrapped cake, which accelerates drying.

Why is my frosting greasy or loose?

Loose frosting often comes from butter that was too warm, cream added too quickly, or a warm room. Peanut butter also softens some frostings because it adds fat.

To correct it, chill the frosting briefly, then rewhip. If it is still loose, add a small amount of powdered sugar and mix again. Add only enough to restore structure, or the frosting can become overly sweet.

Why is my frosting curdled?

Curdling usually means the mixture lost its emulsion, often from temperature mismatch. If the butter is cold, the frosting can look lumpy. If the butter is too warm, the frosting can look separated and shiny.

Try bringing the frosting to a moderate temperature and whipping again. Small corrections work best. Extreme heat or extreme chilling can make it harder to recover.

How should you store peanut butter layer cake safely?

For conservative food safety, refrigerate the cake within 24 hours because the frosting includes cream. If your kitchen is warm, refrigerate sooner.

Short-term storage

• Room temperature: acceptable for a short period, such as several hours for serving, depending on room temperature and how soft the frosting becomes.
• Refrigerated: store covered to prevent drying and odor absorption.

Cold cake is firmer and can seem less moist because butter and peanut butter solidify. For a softer bite, let slices sit at room temperature for 20 to 40 minutes before eating, depending on the temperature of your kitchen.

Freezing

You can freeze unfrosted layers, wrapped tightly, for longer storage. For a frosted cake, freezing can work, but the frosting texture may change slightly when thawed, depending on the fat content and how well the cake was wrapped.

For best results, freeze the cake until firm, then wrap well. Thaw in the refrigerator overnight, still wrapped, to reduce condensation.

What substitutions are reasonable, and which ones change the result?

Can I make a buttermilk substitute?

Yes, but results can vary. A common substitute is milk with an acid added, then rested briefly. This can mimic acidity, but it does not fully replicate cultured buttermilk’s thickness and flavor. If you substitute, expect slight differences in rise and tenderness.

Can I use salted butter?

Yes, but reduce added salt. Salt level becomes harder to predict because peanut butter also varies in saltiness. Adjust cautiously, especially in frosting.

Can I make this as a sheet cake or cupcakes?

Yes, but bake time and heat transfer will change. Sheet cakes bake faster than thick layers, and cupcakes bake faster still. Use doneness cues rather than time alone. For cupcakes, fill liners about two-thirds full and start checking earlier.

Frequently Asked Questions

How do I keep peanut butter cake from sticking to the pans?

Grease the pans and line the bottoms with parchment. Let the cakes cool 15 to 20 minutes in the pans before turning out. Turning out too early can tear the cake; turning out too late can increase sticking as steam condenses.

Can I reduce the sugar without harming the texture?

You can reduce sugar slightly, but large reductions can make the cake drier and less tender. Sugar helps retain moisture and supports a soft crumb. If you reduce, do it modestly and expect subtle changes in browning and texture.

Why does my peanut butter cake taste muted?

Peanut butter flavor can fade if the peanut butter is mild, if the salt level is low, or if the cake is served very cold. A small amount of salt in both batter and frosting improves clarity. Let the cake warm slightly before serving for a fuller flavor.

How thick should the frosting layer be between the cakes?

Aim for an even layer thick enough to cover the surface without squeezing out when stacked. Too thick can encourage sliding, especially in a warm room. If you want a taller filling, chill the cake after stacking to set it.

Can I make the cake layers ahead of time?

Yes. Bake the layers, cool completely, then wrap tightly. Store at room temperature for a short period if your kitchen is cool, or refrigerate for longer holding. For the cleanest slicing and easiest frosting, chilled layers are often simpler to handle.

How long can the frosted cake sit out during serving?

For conservative handling, keep the cake out only as long as needed for serving, then return it to the refrigerator. Warm rooms soften buttercream quickly and increase food safety risk over time, especially with cream in the frosting.

What should I do if my frosting is too sweet?

Salt can balance sweetness slightly, and peanut butter flavor can help, but there is a limit. If it is already made, the best correction is to add a bit more peanut butter and rewhip, keeping in mind that extra peanut butter can soften the frosting. Chilling and rewhipping can restore structure if needed.

Can I add chocolate without changing the cake structure?

Yes. Chocolate decorations such as a thin drizzle or a simple ganache topping can be added without changing the cake layers. If you fold chocolate chips into the batter, they can slightly tighten the crumb and affect rise, depending on quantity and chip size.

Why does my cake crumble when I slice it?

Crumbly cake often points to overbaking, too much flour, or inadequate cooling and setting time. Let the cake cool fully and, if possible, chill it briefly before slicing for cleaner cuts. Use a sharp serrated knife and gentle sawing motions without pressing down.