Key Lime Dump Cake With a Creamy Condensed Milk Filling
Sweetened condensed milk gives this key lime dump cake its creamy filling. Lime juice supplies the tartness, and a cake-mix topping bakes into a tender, golden layer. Serve the dessert warm and the filling will be soft enough to spoon. Chill it for a few hours and it will hold together better when cut, though it will remain softer than a traditional key lime pie.
The method is simple, but the order matters. The condensed milk and lime juice need to be mixed before they go into the baking dish. The dry cake mix then goes over the filling, followed by butter distributed across the surface. That small amount of attention helps prevent dry patches in the topping without turning the recipe into a conventional cake.
What gives the filling its texture
Sweetened condensed milk is milk that has been concentrated and sweetened. It is thick straight from the can, so it gives the filling body without a separate custard-making step. Lime juice brightens its sweetness and helps it thicken further. Sour cream adds a little more body and keeps the filling from tasting overly sweet.
The filling will not behave exactly like key lime pie filling. This version has no eggs and bakes beneath a cake topping, so it stays creamy rather than setting into a firm custard. It also changes noticeably with temperature. Warm from the oven, it may spread as you scoop it. Once refrigerated, it becomes firmer and easier to serve in neat portions.
Bottled key lime juice is convenient and gives a consistent tart flavor. Fresh key limes work too, though juicing enough of the small fruit takes time. Regular Persian limes are a practical substitute. Their flavor is somewhat different, but they still make a good lime dessert. If using fresh fruit, zest the limes before squeezing them.
Key lime dump cake recipe
This recipe makes one 9-by-13-inch cake, about 12 servings. Allow roughly 15 minutes to assemble it and 40 to 50 minutes to bake. For firmer slices, add at least 3 hours of chilling time.
Ingredients
For the filling
- 2 cans (14 ounces or 397 grams each) sweetened condensed milk
- 3/4 cup (180 milliliters) key lime juice or regular lime juice
- 1/2 cup (120 grams) sour cream
- 1 tablespoon finely grated lime zest, optional
For the topping
- 1 box (about 15.25 ounces or 432 grams) yellow or white cake mix
- 3/4 cup (12 tablespoons or 170 grams) unsalted butter, melted
For serving, optional
- Whipped cream
- Additional lime zest
Use sweetened condensed milk, not evaporated milk. Evaporated milk is unsweetened and much thinner; it will not produce the same filling.
Instructions
Heat the oven. Set a rack in the center of the oven and preheat to 350°F (175°C). Lightly grease a 9-by-13-inch baking dish.
Mix the filling. In a large bowl, whisk the sweetened condensed milk, lime juice, sour cream, and optional zest until smooth. Pour the mixture into the prepared dish and spread it evenly.
Add the cake mix. Sprinkle the dry cake mix over the filling in an even layer. Do not stir it into the filling. Break up any large clumps with your fingers.
Cover with butter. Drizzle the melted butter slowly over the cake mix, aiming to cover as much of the surface as possible. A spoon can help direct it toward bare spots. A few small dry-looking areas are less troublesome than large patches of uncovered mix.
Bake. Bake for 40 to 50 minutes, until the topping is golden and the filling bubbles around the edges. The center may still move slightly when the dish is gently shaken. If the top browns before the edges bubble, loosely cover the dish with foil for the remaining baking time.
Cool before serving. Let the cake stand for at least 30 minutes if serving it warm. For firmer portions, cool it, cover it, and refrigerate for at least 3 hours. Add whipped cream or extra zest just before serving, if desired.
Getting the topping and filling right
A dump cake asks the butter to moisten the dry mix as it bakes. Butter poured in one spot can leave a floury patch elsewhere, so take a moment to spread it across the whole dish. There is no need to stir the layers together. Keeping them separate lets the topping bake above the creamy filling.
Cake mixes vary slightly in weight and composition. A standard box close to 15.25 ounces works here; check the package rather than assuming every box is the same size. Yellow cake mix gives the topping a buttery flavor, while white cake mix keeps it a little more neutral. Either lets the lime filling remain the main flavor.
The filling may look loose when it first comes out of the oven. Bubbling edges and a baked, golden topping are better signs of doneness than expecting the center to look firm. Give the dish time to cool before judging its texture. Cutting into it immediately will produce a soft serving, which is pleasant with a spoon but difficult to lift as a slice.
Lime juice also deserves a measured hand. The recipe uses enough to give the condensed milk a clear tang without making the filling excessively sharp. If fresh limes are especially tart, taste the mixture before pouring it into the dish. The flavor will be sweeter once paired with the cake topping, but it should already taste distinctly of lime.
Serving and storing the cake
Serve the cake warm in bowls for the softest texture. After chilling, cut it with a knife and lift portions with a wide spatula. Even cold, the filling is creamy, so expect a dessert that sits somewhere between a cake and a spoonable pudding rather than a tidy layer cake.
A little unsweetened or lightly sweetened whipped cream works well on top. Extra lime zest adds aroma without making the filling more acidic. Neither is necessary if the cake is being served straight from the baking dish.
Cover leftovers and refrigerate them promptly. They will keep for up to 4 days. The topping softens somewhat in the refrigerator as it absorbs moisture from the filling. For a warm serving, heat an individual portion briefly in the microwave; it will become softer again. Keep whipped cream separate until serving.
A creamy lime dessert with two ways to serve it
The same pan offers two useful textures. Warm key lime dump cake is loose, creamy, and easy to spoon into bowls. Chilled cake is firmer and better suited to slices. In both cases, sweetened condensed milk provides the filling’s sweetness and body, while lime juice keeps the dessert bright beneath its golden topping.
