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Peanut Butter Sheet Cake with Fluffy Peanut Butter Frosting

A soft, tender peanut butter sheet cake topped with thick, fluffy peanut butter frosting. Perfect for gatherings and nostalgic dessert cravings.
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Prep Time 15 minutes
Cook Time 28 minutes
Total Time 43 minutes
Servings: 16 squares
Course: Cake, Dessert
Cuisine: American
Calories: 390
Ingredients Equipment Method Notes

Ingredients
  

Cake Ingredients
  • 2 cups all-purpose flour
  • 2 cups granulated sugar
  • 1/2 tsp salt
  • 1 tsp baking soda
  • 1 cup water
  • 1/2 cup unsalted butter
  • 1/2 cup creamy peanut butter
  • 2 eggs
  • 1/2 cup sour cream
  • 1 tsp vanilla extract
Fluffy Peanut Butter Frosting
  • 1/2 cup unsalted butter, softened
  • 1/2 cup creamy peanut butter
  • 4 cups powdered sugar
  • 1/4-1/2 cup milk or heavy cream
  • 1 tsp vanilla extract

Equipment

  • Saucepan
  • Mixing bowls
  • Electric mixer
  • 9×13-inch pan

Method
 

  1. Preheat oven to 350°F and grease a 9x13-inch pan.
  2. Mix flour, sugar, salt, and baking soda in a large bowl.
  3. Heat water, butter, and peanut butter until melted; add to dry ingredients.
  4. Add eggs, sour cream, and vanilla; mix until smooth.
  5. Bake 22–28 minutes until a toothpick comes out clean.
  6. Make frosting by whipping butter and peanut butter, then adding powdered sugar and milk.
  7. Frost cooled cake and slice into squares.

Notes

Use heavy cream for extra fluffy frosting.