High Altitude Key Lime Pie Sheet Cake

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This high altitude key lime pie cake is a cool and creamy dessert that starts with a fluffy vanilla cake baked on top of a graham cracker crust. The cake is lightly soaked with milk, then topped with homemade lime pudding and fresh whipped cream.

You might also love these recipes for orange creamsicle cake, citrus sour cream pie, and key lime pie cupcakes.

Key lime pie sheet cake with whipped cream flowers and lime slices on top.

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Why You’ll Love This Recipe

Everything Homemade. Today’s recipe for key lime pie cake is completely made from scratch. There’s no boxed cake mix, no jello, no instant pudding or artificial dyes, and no Cool Whip. Just simple, delicious ingredients.

Make Ahead. This is a wonderful dessert to make for a party, potluck or summer get together, since you can assemble it in the morning, and just keep it refrigerated until ready to serve that afternoon or evening.

Tastes Like Key Lime Pie. Although today’s recipe is based on my lemon pudding poke cake, the layer of graham cracker crust underneath the cake really adds that key lime pie flavor and texture.

High Altitude Tested. I develop all the recipes on my site for Denver’s altitude of 5,280 feet. If you’re at a lower or higher elevation, please see my FAQs for guidance on adjusting recipes for your altitude.

Slice of key lime pie cake, with layers of graham cracker crust, vanilla cake, lime pudding, and whipped cream.

See the recipe card at the end of the post for the full ingredients list and instructions.

Ingredients

Vanilla Cake

For the cake, I’m using my favorite recipe for vanilla sheet cake, which is always so soft, fluffy and moist. You’ll need cake flour, sugar, baking powder, salt, eggs, buttermilk, butter, vegetable oil and vanilla extract.

Lime Pudding

The lime pudding is a simple combination of sugar, lime zest and juice, corn starch, egg yolks, milk, and cream. For step by step photos, you can see this recipe for lemon pudding.

Whipped Cream

I made my recipe for stabilized whipped cream, which uses cream cheese to stabilize the whipping cream, so that it doesn’t deflate on top of the cake.

Instructions

Graham Cracker Crust

Preheat the oven to 350 F and position a rack in the center of the oven. Lightly spray a 9×13 inch baking dish with non-stick baking spray.
In a bowl, combine the crushed graham crackers, sugar and salt. Add the melted butter, and stir until moistened and crumbly. Press the crumbs evenly and firmly against the bottom of the prepared baking dish.
Bake the crust for 5 minutes, just to lightly toast the crumbs and seal the crust, so that the cake batter doesn’t displace the crumbs when you pour it into the pan. Set aside to cool the crust slightly while you make the cake batter.

Graham cracker crust pressed into a baking dish.

Vanilla Cake

Make the batter for the Vanilla Sheet Cake as instructed. Carefully pour the batter over the cooled graham cracker crust.
Bake the cake for about 38-45 minutes, until the top springs back when gently touched, and a cake tester or sharp knife inserted in the center comes out clean.
Let the cake cool for 30 minutes. With both the graham cracker crust and the cake layers, the 9×13 pan will be very full, so I recommend using a knife or the sharp edge of an offset metal icing spatula to carefully cut/scrape off the top 1/4 – 1/2 inch of cake. If you don’t do this, your pan may overflow when you pour the pudding on top, or you just won’t be able to use all the pudding.
Next, pour the reserved 1/2 cup of milk over the cake. This will help to keep it moist and soft, since this is a refrigerated cake.
While the cake is baking, you should be cooking the lime pudding, so that it’s ready to pour over the cake at this point.

Lime Pudding

Measure the sugar into a bowl, then zest the limes over the sugar. Use your fingers to rub the lime zest into the sugar.
Cut the limes and juice them into a glass measuring cup to get 1/2 cup of juice, or just use bottled lime juice.
In a medium sized saucepan, whisk together the lime sugar with the corn starch. Whisk in the lime juice until smooth, then whisk in the egg yolks.
Add the milk and the cream, and whisk until combined.
Place the saucepan over medium to medium low heat. Use a silicone spatula to stir the mixture constantly, while gently cooking the pudding. Cook until the pudding starts to thicken enough to coat the spatula, and is just beginning to bubble, but do not let the pudding start boiling hard. This should take about 15 minutes of cooking for the pudding to thicken. Remove from the heat.
Set a mesh strainer over a bowl, and press the pudding through the strainer to remove the zest.
Place a piece of plastic wrap over the bowl, with the plastic resting right against the surface of the pudding to prevent a skin from forming. Let cool at room temperature for 30 minutes.
At this point, the cake should have cooled for 30 minutes, and you’ve already poured the reserved 1/2 cup of milk over the cake.
Pour the warm pudding over the cake, and spread it out into an even layer.
Set the cake in the refrigerator to chill for 1 1/2 – 2 hours, until the cake is cool and the pudding is set.

Vanilla sheet cake with holes poked in it.

Whipped Cream

In the bowl of your stand mixer fitted with the paddle attachment (or using a hand-held electric mixer), beat the cold cream cheese with the powdered sugar for about 1 minute on medium speed, until smooth.
Scrape the bowl down, then add the vanilla and about 1/4 cup of the cream. Beat on medium speed for 30-60 seconds to smooth out any lumps of cream cheese.
Add the remainder of the cream, and switch to the whisk attachment. (You can also continue to use the paddle attachment, but it will take a few minutes longer).
Whip the cream on medium high speed for several minutes, stopping to scrape the bowl down once or twice, until thick fluffy peaks form that hold their shape.
Spread or pipe the whipped cream over the lime pudding. I used tip 1M, to pipe pretty drop flowers all over the cake. If you like, decorate with fresh lime slices and crumbled graham crackers.

Be sure to read all of my BAKING FAQs where I discuss ingredients, substitutions and common questions with cake making, so that you can be successful in your own baking! I also suggest reading these comprehensive posts on making Perfect American Buttercream, How to Stack, Fill, Crumb Coat and Frost Layer Cakes and How to Use Piping Bags.

Frequently Asked Questions

How should I store the leftover cake?

Store the leftover cake in the refrigerator, with the pan covered with plastic wrap, or individual pieces stored in an airtight container, for up to 3 days.

Why doesn’t the lime juice curdle the milk in the pudding?

Thanks to the high fat content of whole milk and heavy whipping cream, the acid in the lime juice is stabilized, so it won’t curdle. You also need to heed the instructions and not let the pudding boil. Take it off the heat as soon as it thickens, but before it begins to boil hard.

Citrus sour cream pie with whipped cream and sliced lemons, limes and oranges. — Citrus Pie

Lemon cake decorated with dried lemon slices. — Citrus Pie

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