If you’re a peanut butter lover, this soft sheet cake delivers plenty of peanut butter flavor from the cake itself and its rich, creamy frosting. Baked in a jellyroll pan, it makes a generously sized dessert that is easy to prepare and perfect for sharing.

Ingredients

For the Peanut Butter Sheet Cake

• 2 cups all-purpose flour
• 2 cups granulated sugar
• 1/2 teaspoon baking soda
• 1/4 teaspoon salt
• 1/2 cup peanut butter
• 1/4 cup vegetable oil
• 2 eggs
• 1/2 cup buttermilk
• 1 teaspoon vanilla extract

For the Peanut Butter Frosting

• 2 sticks (1 cup) butter, softened
• 3/4 cup peanut butter
• 3 cups confectioners’ sugar
• 3 to 4 tablespoons milk
• 2 tablespoons instant vanilla pudding mix

Instructions

Make the Cake

1. Prepare the Oven and Pan: Preheat the oven to 350°F. Grease a 10 × 15 × 1-inch jellyroll pan thoroughly and set it aside.
2. Mix the Dry Ingredients: In a large bowl, whisk together the flour, sugar, baking soda, and salt until evenly combined.
3. Prepare the Butter Mixture: Place 1 1/2 sticks of butter and 1 cup of water in a medium saucepan. Bring the mixture to a simmer, stirring as needed until the butter has completely melted.
4. Add the Peanut Butter: Whisk the 1/2 cup peanut butter and vegetable oil into the warm butter mixture. Once combined, pour this mixture into the bowl containing the dry ingredients and stir to incorporate.
5. Add the Remaining Wet Ingredients: In a separate bowl, whisk together the eggs, buttermilk, and vanilla extract. Add this mixture to the flour mixture and stir until the batter is thoroughly combined.
6. Fill the Pan: Pour the prepared batter into the greased jellyroll pan and spread it evenly.
7. Bake: Place the cake in the preheated oven and bake for approximately 22 to 26 minutes. Check for doneness by inserting a toothpick into the center; it should come out clean when the cake is ready.
8. Cool: Remove the cake from the oven and allow it to cool before applying the frosting.

Prepare the Peanut Butter Frosting

1. Beat the Peanut Butter and Butter: Using an electric mixer, beat the softened butter and peanut butter together until the mixture is smooth and creamy.
2. Add the First Portion of Sugar and Milk: Add half of the confectioners’ sugar along with half of the milk. Beat again until the frosting becomes smooth.
3. Finish the Frosting: Add the remaining confectioners’ sugar, the rest of the milk, and the instant vanilla pudding mix. Continue beating until everything is smooth and well incorporated. If the frosting is too thick, add a little additional milk until it reaches a spreadable consistency.
4. Frost the Cake: Spread the finished peanut butter frosting evenly over the cooled cake.

Important Recipe Note

The original ingredient list for the cake does not separately list the 1 1/2 sticks of butter and 1 cup of water that are specified in the preparation instructions. The amounts have been retained here exactly as they appear in the original directions.