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An overhead image of a key lime sheet cake with a slice being removed from the middle of it.
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Key Lime Pie Sheet Cake

This easy Key Lime Pie Sheet Cake combines a buttery graham cracker crust, fluffy white cake, creamy key lime filling, and delicious frosting for a bright, crowd-pleasing dessert that’s perfect for summer or holiday gatherings.
Prep Time30 minutes
Cook Time30 minutes
Chilling Time8 hours
Total Time9 hours
Course: Dessert
Cuisine: American
Servings: 12 servings
Author: Amy Nash

Equipment

Ingredients

Graham Cracker Crust

  • 6 cups finely crushed graham crackers divided
  • 1 cup (227g) salted butter melted

Cake

  • 1⅓ cups (188g) all-purpose flour
  • 1½ cups (300g) granulated sugar
  • 1¼ teaspoons baking powder
  • ½ teaspoon salt
  • ½ cup salted butter room temperature
  • 4 large egg whites room temperature
  • ¾ cup (6 ounces) buttermilk room temperature
  • ¼ cup (60g) sour cream or greek yogurt room temperature
  • 1 Tablespoon vegetable oil
  • 1 Tablespoon key lime juice
  • 1 teaspoon clear vanilla extract

Key Lime Pie Layer

  • 1½ cups (12 ounces) heavy cream
  • 3 (8-ounce) packages cream cheese room temperature
  • 1½ (14-ounce) cans sweetened condensed milk (21 ounces total)
  • ¾ cup key lime juice
  • 1 Tablespoon lime zest
  • 1 teaspoon clear vanilla extract

Frosting

  • 6 cups (680g) powdered sugar
  • 1 cup salted butter softened
  • ¼ cup heavy cream
  • 2 Tablespoons lime zest
  • 4 teaspoons clear vanilla extract
  • ½ teaspoon salt

Extras/Garnishes

  • 30 round key lime slices
  • Additional graham cracker crumbs
  • Lime zest

Instructions

  • Preheat the oven to 350°F.
  • In a food processor, pulse graham crackers until a sandy consistency. Add the melted butter and mix until evenly moistened.
    6 cups finely crushed graham crackers, 1 cup (227g) salted butter
  • Press 3 cups of the graham cracker mixture evenly into a 9x13-inch baking dish. Set aside. Reserve the extra graham crackers for later.
  • In a bowl, add the flour, granulated sugar, baking powder, and salt until mixed. In a stand mixer, mix the butter, egg whites, buttermilk, sour cream, oil, key lime juice, and clear vanilla extract until well combined. Then add the flour mixture in and mix just until combined. Do not overmix.
    1⅓ cups (188g) all-purpose flour, 1½ cups (300g) granulated sugar, 1¼ teaspoons baking powder, ½ teaspoon salt, ½ cup salted butter, 4 large egg whites, ¾ cup (6 ounces) buttermilk, ¼ cup (60g) sour cream or greek yogurt, 1 Tablespoon vegetable oil, 1 Tablespoon key lime juice, 1 teaspoon clear vanilla extract
  • Pour the cake batter into the prepared pan (on top of the graham cracker layer). Bake for 30-35 minutes or until golden brown and a toothpick comes out clean in the middle. Spread 2 cups of the reserved graham cracker/butter mixture evenly across the top of the warm cake. Set aside to cool.
  • To make the key lime layer, in a medium-sized bowl, beat the cold heavy whipping cream with a hand mixer until medium-stiff peaks form. Set aside.
    1½ cups (12 ounces) heavy cream
  • In a different bowl, beat the cream cheese, sweetened condensed milk, key lime juice, key lime zest, and clear vanilla extract together. Once completely mixed, add the whipped cream into the cream cheese mixture gently.
    3 (8-ounce) packages cream cheese, 1½ (14-ounce) cans sweetened condensed milk, ¾ cup key lime juice, 1 Tablespoon lime zest, 1 teaspoon clear vanilla extract
  • Pour the pie batter on top of the graham cracker layer in the pan. Let it set in the fridge for at least 8 hours or overnight to set up.
  • To make the frosting, slowly beat the powdered sugar, butter, heavy whipping cream, key lime zest, clear vanilla, and salt until smooth. Scoop it into a piping bag fitted with a star tip (I used the size 4B tip) and pipe dollops around the cake.
    6 cups (680g) powdered sugar, 1 cup salted butter, ¼ cup heavy cream, 2 Tablespoons lime zest, 4 teaspoons clear vanilla extract, ½ teaspoon salt
  • Add round lime slices in between dollops, sprinkle extra graham cracker crumb mixture or plain crumbs along the edge, and add additional lime zest.
    30 round key lime slices, Additional graham cracker crumbs, Lime zest

Notes

  • Chill overnight so the pie layer fully sets and slices cleanly.
  • Garnish just before serving to keep lime slices fresh and crumbs crunchy.
  • Freeze for 30 minutes before slicing for sharp, neat cuts.
  • Use clear vanilla to keep the cake and frosting bright.
  • Double the recipe easily for a crowd using two 9x13 pans or a jelly roll pan.
 

Storage & Make Ahead

  • Store: Keep covered in the fridge for 5-7 days.
  • Freeze: Wrap slices tightly and freeze in a sealed container for up to 2 months.
  • Make Ahead: Make the day before serving to give the filling time to set properly.

Nutrition

Calories: 873kcal | Carbohydrates: 99g | Protein: 5g | Fat: 53g | Saturated Fat: 33g | Polyunsaturated Fat: 2g | Monounsaturated Fat: 13g | Trans Fat: 2g | Cholesterol: 146mg | Sodium: 588mg | Potassium: 128mg | Fiber: 0.5g | Sugar: 86g | Vitamin A: 1759IU | Vitamin C: 6mg | Calcium: 88mg | Iron: 1mg

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