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Old-Fashioned Peanut Butter Cake Recipe with Warm Peanut Butter Icing

Old-Fashioned Peanut Butter Cake

A tender Southern-style peanut butter sheet cake baked in a 9 x 13-inch pan and finished with warm peanut butter icing. It makes approximately 12–16 servings and is especially delicious while the icing is still slightly soft.
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Prep Time 15 minutes
Cook Time 30 minutes
Total Time 1 minute
Servings: 12 servings
Ingredients Method Notes

Ingredients
  

Cake
  • 2 cups Granulated sugar
  • 2 cups All-purpose flour
  • 1 teaspoon Baking soda
  • 1/2 teaspoon Salt
  • 1 cup Water
  • 3/4 cup Unsalted butter
  • 1/2 cup Creamy peanut butter
  • 1/2 cup Vegetable oil
  • 2 Large eggs
  • 1/2 cup Buttermilk
  • 1 teaspoon Vanilla extract
Peanut Butter Icing
  • 1/2 cup Unsalted butter
  • 1/2 cup Creamy peanut butter
  • 6 tablespoons Milk
  • 1 pound, about 3 3/4 to 4 cups Confectioners’ sugar
  • 1 teaspoon Vanilla extract

Method
 

Step-by-Step
  1. Heat the oven to 350°F and grease a 9 x 13-inch baking pan.
  2. Whisk the sugar, flour, baking soda, and salt together in a large mixing bowl.
  3. In a saucepan, heat the water, butter, peanut butter, and vegetable oil until the butter and peanut butter melt and the mixture is hot. Do not let it boil vigorously.
  4. Pour the hot peanut-butter mixture over the dry ingredients and stir until mostly smooth.
  5. Add the eggs, buttermilk, and vanilla, then mix just until combined.
  6. Pour the batter into the prepared pan and bake for 30–35 minutes, until the center is set and a toothpick comes out with only a few moist crumbs.
  7. While the cake bakes or immediately after it comes out, heat the icing butter, peanut butter, and milk in a saucepan until melted and smooth.
  8. Remove the saucepan from the heat and gradually beat in the confectioners’ sugar and vanilla until the icing is thick but spreadable.
  9. Spread the warm icing over the warm cake, then let the cake cool before slicing.

Notes

Use regular creamy peanut butter rather than natural peanut butter for the most consistent batter and icing. Frost the cake while warm, and avoid overbaking so the crumb stays soft and moist.