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Key Lime Cake

This Key Lime Cake features three layers of fluffy white cake with a hint of lime, a buttery graham cracker crumble in between each layer, and a sweet yet tangy key lime buttercream frosting… classic summer flavors and perfect for any gathering!

Course Dessert
Cuisine American
Keyword Key lime cake, Summer cake
Prep Time 1 hour
Cook Time 20 minutes
Total Time 1 hour 20 minutes
Servings 1 8-inch 3-layer cake

Ingredients

For the Cake:

  • 3 cups cake flour
  • 1.5 teaspoons baking powder
  • 1.5 teaspoons baking soda
  • 1/2 teaspoon salt
  • 1 cup (2 sticks) unsalted butter, room temperature
  • 1 ¾ cups sugar
  • ½ cup sour cream, room temperature
  • 2 teaspoons vanilla extract
  • ½ cup milk, room temperature
  • 2 tablespoons vegetable oil
  • 8 tablespoons key lime juice (8-10 key limes)
  • 5 egg whites, room temperature

For the Graham Cracker Crumbs:

  • 2 cups graham cracker crumbs
  • 2 tablespoons sugar
  • ½ cup 1 stick butter, melted and slightly cooled

For the frosting:

  • 1.5 cups (3 sticks) unsalted butter, softened
  • 1 cup shortening
  • 1/4 teaspoon salt
  • 6-8 cups powdered sugar
  • 3 tablespoons key lime juice (3-4 key limes)
  • ¼ cup sweetened condensed milk
  • 1-2 tablespoons hot water
  • Green food coloring gel

For decoration:

  • 1-2 cups heavy whipping cream, cold
  • 1 tablespoon sugar
  • Limes slices for garnish

Instructions

For the Graham Cracker Crumbs:

  1. In a small bowl, combine the graham cracker crumbs, sugar, and melted butter and stir until well combined and crumbly. Spread mixture onto a cookie sheet lined with parchment paper. Bake at 350° F for about 5 minutes, then remove and set aside to cool.

For the Cake:

  1. Preheat oven to 350º F. Lightly grease and flour 3 8-inch round cake pans lined with parchment paper (you can also use 2 9-inch but will want to bake longer).
  2. In a large bowl, sift together the cake flour, baking powder, baking soda, and salt. Set aside.
  3. In a small bowl, stir together the milk, vegetable oil, and key lime juice. Set aside.
  4. With your mixer (I use paddle attachment), cream together the butter and sugar on medium-high speed until very light and fluffy (3- 5 minutes).
  5. Add sour cream and vanilla extract and beat until well combined, about one minute.
  6. Starting and ending with flour, with your mixer on LOW speed, alternately add flour mixture and milk mixture to the creamed butter until just combined.
  7. In a large clean bowl, (I transfer the batter to a bowl and clean my mixing bowl thoroughly to use here with my wire attachment) beat the egg whites until stiff peaks form.
  8. Gently fold 1/3 of the whites into batter, followed by another 1/3 of the egg whites, and then the remaining whites. Divide evenly into prepared pans.
  9. Bake at 350ºF for 18 to 20 minutes, or until the cake slightly pulls away from the sides or until a toothpick inserted into the center of the cake comes out clean.
  10. Let cool in pans 10 minutes and then remove to a wire rack to cool completely.

For the Frosting:

  1. With your mixer on medium speed (I use paddle attachment), beat the butter and shortening on medium speed until smooth, about 1 minute.
  2. Add salt and half of powdered sugar and beat on low speed until combined.
  3. Add lime juice and sweetened condensed milk and beat until combined.
  4. Add remaining powdered sugar and beat until combined. Once combined, add hot water and beat on medium speed for 5 minutes. Dip a toothpick in your gel food coloring and add to frosting. Beat on medium to combine. Continue to add coloring until you reach the desired color, and beat on medium speed for another 5 minutes.

For whipped cream:

  1. Add heavy cream and sugar to bowl of mixer fitted with the whisk attachment and beat on medium-high speed until stiff peaks form.

To Assemble:

  1. Place one cake layer upside down on a cake plate or stand and spread 1-2 cups of frosting on cake. Add a layer on graham cracker crumbs on top. Repeat with second layer. Add third cake layer and frost a thin layer on the sides and top (crumb coat). I usually put it in the fridge or freezer at this point for 5-10 minutes and then add additional frosting to the top and sides.
  2. To decorate as pictured, add remaining graham cracker crumbs to the bottom of the cake. Add whipped cream to a pastry bag fitted with tip #1M, and pipe whipped cream swirls around the top of the cake. Add halved sliced limes to every other whipped cream swirl, if desired.

Recipe Notes

Store covered at room temperature for 1-2 days.