Easy Key Lime Dump Cake Recipe With Creamy Lime Filling

Key Lime Pie Flavor in an Easy Dump Cake

Key lime pie has a creamy, tart filling and a crumbly crust. This key lime dump cake keeps the lime-and-condensed-milk flavor but trades the crust for a golden cake topping. It comes out of the oven soft enough to serve with a spoon. After a night in the refrigerator, the filling firms up and the portions hold together better.

“Dump cake” describes the assembly: spread the filling in a baking dish, scatter dry cake mix over it, and add butter before baking. There’s no cake batter to mix. The one step worth taking slowly is adding the butter. Dry patches of cake mix won’t bake into a tender topping unless they get enough moisture.

Key Lime Dump Cake Recipe

Yield: About 10 servings
Prep time: 15 minutes
Bake time: 45 to 55 minutes
Total time: About 1 hour 10 minutes, plus cooling
Equipment: 9-by-13-inch baking dish, mixing bowl, whisk

Ingredients

For the lime filling

• 2 cans (14 ounces/396 g each) sweetened condensed milk
• 1 cup (240 g) full-fat sour cream
• ¾ cup (180 ml) key lime juice, bottled or freshly squeezed
• 1 tablespoon finely grated lime zest, optional
• ¼ teaspoon fine salt

For the topping

• 1 box (about 15 ounces/425 g) white or yellow cake mix
• ¾ cup (12 tablespoons/170 g) unsalted butter, melted

For serving, optional

• Lightly sweetened whipped cream
• Lime zest or thin lime wedges

Instructions

1. Heat the oven. Set a rack in the center of the oven and heat it to 350°F (175°C). Lightly grease a 9-by-13-inch baking dish.

2. Mix the filling. Whisk the sweetened condensed milk, sour cream, lime juice, optional zest, and salt in a bowl until smooth. The mixture will thicken slightly as the lime juice is incorporated. Spread it evenly in the prepared dish.

3. Add the cake mix. Sprinkle the dry cake mix evenly over the filling. Break up any large clumps with your fingers. Do not stir the cake mix into the filling.

4. Add the butter. Drizzle the melted butter slowly over the surface, aiming to cover as much of the dry mix as possible. A spoon helps direct it into bare spots. Leave the layers undisturbed.

5. Bake. Bake for 45 to 55 minutes, until the topping is golden and the filling is bubbling around the edges. If the top browns quickly while broad areas still look powdery, loosely cover the dish with foil for the remaining bake time.

6. Cool before serving. Let the cake stand for at least 30 minutes for warm, scoopable servings. For firmer portions, cool it completely, cover, and refrigerate for at least 4 hours.

The filling will be soft when the dish first comes out of the oven. A spoonful should show a creamy lime layer beneath the cake topping; it won’t have the clean, firm edge of a slice of pie.

Getting the Lime Flavor Right

Key limes are small and aromatic, but squeezing enough of them for ¾ cup of juice takes time. Bottled key lime juice is a practical choice here. Check the label for unsweetened juice, since a sweetened lime drink would change the filling. Fresh Persian limes, the larger limes found in most grocery stores, also work. The dessert will still have the familiar tart, creamy character, though the flavor won’t be identical to one made with key limes.

Taste the juice before adding it, especially if the bottle has been open for a while. Lime juice that tastes stale or bitter won’t improve in the oven. If using fresh fruit, grate the zest before cutting and squeezing the limes. Take only the colored outer layer; the white pith underneath can taste bitter.

Use sweetened condensed milk, not evaporated milk. Condensed milk supplies both sweetness and body to the filling. Evaporated milk is unsweetened and much thinner, so it isn’t a direct substitute. Full-fat sour cream adds richness and softens the sharpness of the lime. The finished filling should taste tangy, but it is still a sweet dessert.

How the Cake Topping Bakes

A dump cake topping behaves differently from a conventional cake batter. The dry mix absorbs moisture from the filling below and butter from above. Some spots bake up tender, while the exposed surface becomes lightly crisp. That uneven texture is part of the dessert, but large pockets of untouched powder are not.

Sprinkle the mix in a thin, even layer rather than pouring it into a mound and spreading it afterward. Then drizzle the butter across the whole dish. Melted butter makes coverage easier than butter cut into a few thick slices, though either method can leave a dry spot if the butter is concentrated in one area. Don’t stir after adding the topping: mixing would pull the lime filling into the cake mix and blur the two layers.

White cake mix lets the lime stand out. Yellow cake mix gives the topping a slightly richer flavor and a deeper color. Either is suitable. Box sizes vary, so a mix close to 15 ounces is the best fit for the amounts above. A substantially larger box may need more butter to moisten the surface.

Look for bubbling at the edges as well as color on top. The center may still feel soft because the filling remains creamy. If a small patch of powder remains near the end of baking, you can dab it with a little melted butter and return the dish to the oven briefly. There’s no need to keep baking until the filling becomes firm; it will thicken further as it cools.

Serving and Storing the Cake

Warm servings are best scooped into bowls. The contrast between the soft lime filling and the golden topping is especially noticeable then, and a little whipped cream can mellow the tartness. Let the dish rest before scooping so the filling isn’t piping hot and runny.

For neater portions, refrigerate the cooled cake for at least 4 hours or overnight. Chilling firms the filling, although the topping loses some of its crispness in the refrigerator. That trade-off is useful to know if you’re making dessert ahead for guests: choose warm scoops for texture or chilled portions for easier serving.

Cover leftovers and refrigerate them promptly. Because the dessert contains dairy, don’t leave it at room temperature for more than 2 hours. Eat refrigerated leftovers within 3 to 4 days. You can serve them cold or warm individual portions briefly in the microwave; reheating will soften the topping.

This is a good key lime pie alternative when you want the tart, creamy filling without making a crust or waiting for a pie to set before serving. Keep the cake mix and butter evenly distributed, bake until the edges bubble, and decide whether to serve it warm or chilled based on the texture you want.