Tips for Success
Use a smooth, creamy peanut butter for best results—natural peanut butter may cause texture issues. Pour the frosting over the cake while both are warm so it spreads evenly and sets beautifully. Don’t overmix the batter to keep the cake light and tender. Let the cake cool slightly before frosting to avoid sinking or cracking.
Ingredients
For the Cake:
2 cups all-purpose flour
2 cups granulated sugar
1/2 teaspoon salt
1 teaspoon baking soda
1 cup water
1/2 cup unsalted butter
1/2 cup creamy peanut butter
1/2 cup buttermilk
2 large eggs
1 teaspoon vanilla extract
For the Frosting:
1/2 cup unsalted butter
1/2 cup creamy peanut butter
1/3 cup milk
1 teaspoon vanilla extract
3 to 3 1/2 cups powdered sugar
Directions
Preheat the oven to 350°F (175°C). Grease a 9×13-inch sheet pan and set aside. In a large bowl, whisk together flour, sugar, salt, and baking soda. In a saucepan, combine water, butter, and peanut butter over medium heat, stirring until melted and smooth. Pour the hot mixture into the dry ingredients and stir to combine. Add buttermilk, eggs, and vanilla, and mix until just combined. Pour into the prepared pan and smooth the top. Bake for 25–30 minutes, or until a toothpick comes out clean.
While the cake bakes, make the frosting. In a saucepan over medium heat, melt butter and peanut butter. Stir in milk and vanilla, then remove from heat and whisk in powdered sugar until smooth and spreadable. Pour the warm frosting over the warm cake and spread evenly. Let the cake cool completely before serving.
Additional Tips or Variations
Top with chopped peanuts or a drizzle of melted chocolate for extra texture and flavor. Add a pinch of cinnamon to the batter for warmth. For a peanut butter and jelly twist, swirl in a few spoonfuls of raspberry or strawberry jam before baking.