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Peanut Butter Sheet Cake pinterest

Peanut Butter Sheet Cake

This crowd-pleasing dessert features a moist, tender crumb infused with rich peanut butter flavor, topped with a decadent frosting that melts in your mouth. Perfect for potlucks, family gatherings, or anytime you need to feed a crowd with minimal fuss.
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Course: Dessert
Cuisine: American
Keyword: Peanut Butter Cake, Sheet Cake, Peanut Butter Dessert, Crowd-Pleasing Dessert
Prep Time: 20 minutes
Cook Time: 25 minutes
Cooling & Frosting Time: 40 minutes
Total Time: 1 hour 25 minutes
Servings: 20 slices
Calories: 375kcal

Equipment

  • 10×15-inch Rimmed Baking Sheet
  • Saucepan
  • Mixing Bowl

Ingredients

For the Cake

  • 2 cups all-purpose flour substitute with 1:1 gluten-free flour blend if needed
  • 2 cups granulated sugar
  • 1 tsp baking soda
  • 1/2 tsp salt
  • 1 cup water
  • 1 cup unsalted butter 2 sticks
  • 1/2 cup creamy peanut butter natural or regular both work
  • 1/4 cup vegetable oil
  • 2 large eggs room temperature
  • 1/2 cup buttermilk or 1/2 cup milk + 1/2 tablespoon vinegar
  • 1 tsp vanilla extract

For the Frosting

  • 1/2 cup unsalted butter 1 stick
  • 1/2 cup creamy peanut butter
  • 1/4 cup milk
  • 4 cups powdered sugar
  • 1 tsp vanilla extract
  • 1/4 tsp salt
  • 1/2 cup chopped peanuts for garnish (optional)

Instructions

  • Preheat your oven to 350°F (175°C). Generously grease a 10×15-inch rimmed baking sheet or jelly roll pan. Pro tip: Line the pan with parchment paper with overhanging edges for easy removal and cleanup.
  • In a large mixing bowl, whisk together the flour, sugar, baking soda, and salt until well combined. Breaking up any clumps now will ensure a smooth, even cake texture later.
  • In a medium saucepan over medium heat, combine water, butter, and peanut butter. Stir constantly until the mixture comes to a boil and ingredients are fully melted and incorporated.
  • Pour the hot peanut butter mixture over the dry ingredients and stir until just combined. A wooden spoon works perfectly here – the batter will be quite thick at this stage.
  • In a small bowl, whisk together the vegetable oil, eggs, buttermilk, and vanilla. Add this mixture to the batter and stir until just combined. Be careful not to overmix – stop when no dry streaks remain for the most tender cake.
  • Pour the batter into your prepared pan, spreading it evenly to the corners. Bake for 22-25 minutes, or until a toothpick inserted in the center comes out clean with a few moist crumbs.
  • While the cake bakes, prepare your frosting. In a saucepan, combine butter, peanut butter, and milk. Heat over medium heat, stirring until smooth. Remove from heat and gradually whisk in powdered sugar, vanilla, and salt until silky and spreadable.
  • Pour the warm frosting over the still-warm cake, spreading quickly as it will begin to set. If using, sprinkle chopped peanuts over the top. Let cool completely before cutting into squares.

Notes

For a richer chocolate variation, add 1/2 cup cocoa powder to the frosting or drizzle melted chocolate over the top. This cake is best served at room temperature but can be gently reheated for 10-15 seconds in the microwave for a more decadent texture.

Nutrition

Calories: 375kcal | Carbohydrates: 45g | Protein: 4g | Fat: 21g | Saturated Fat: 10g | Cholesterol: 55mg | Sodium: 220mg | Fiber: 1g | Sugar: 35g
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