This Peanut Butter Sheet Cake is for true peanut butter lovers. A tender peanut butter cake is finished with a silky, easy-to-make peanut butter frosting that melts in your mouth.
Easy Peanut Butter Sheet Cake
Hi, I’m Marie from Sugar Salt Magic. When I want a wholehearted peanut butter moment, this peanut butter sheet cake is my go-to. The cake is soft, moist and lightly sweet, with a clear peanut butter character. Topped with a pillowy peanut butter buttercream, it’s everything a PB fan could want.
Sheet cakes are ideal for gatherings and make-ahead desserts — they’re quick to prepare and serve just like a layered cake. This recipe bakes in a 9×13-inch pan and yields about 24 servings, though you’ll likely be back for seconds.
The cake and frosting freeze well, so you can keep a slice (or a whole cake) on hand for when cravings strike.
What’s in This Peanut Butter Cake?
Most ingredients are pantry staples. For the cake you’ll need:
- All-purpose flour
- Baking powder
- Salt
- Brown sugar
- Granulated sugar
- Creamy peanut butter
- Vegetable oil
- Vanilla extract
- Eggs
- Whole milk
For the peanut butter buttercream:
- Unsalted butter
- Creamy peanut butter
- Powdered sugar
- Salt
- Vanilla extract
How to Make Peanut Butter Sheet Cake
This is a straightforward mix-and-go recipe. Basic steps:
- Beat together creamy peanut butter, oil, brown and granulated sugar, and vanilla until smooth.
- Add the eggs one at a time, beating well after each addition.
- Whisk the flour, baking powder and salt in a separate bowl. Add one third of the dry mix to the wet ingredients and fold until just combined.
- Alternate adding the milk and the remaining dry ingredients (half the milk, then more flour, then the rest of the milk and flour), folding gently until just combined.
- Pour the batter into a lined 9×13-inch pan, smooth the top and bake about 18–20 minutes, until a toothpick comes out with a few crumbs but no wet batter.
Tips for Making Peanut Butter Sheet Cake
- Use regular creamy peanut butter for the best texture and flavor; natural, oil-separated peanut butter can change the batter consistency.
- The combination of brown and granulated sugar gives the ideal crumb and a subtle caramel note. Using only one type of sugar can make the cake too dense or too dry.
- Whisking the dry ingredients separately helps distribute the leavening and salt evenly and adds a touch of lightness to the flour.
How to Make the Peanut Butter Frosting
Simple steps to a creamy frosting:
- Beat together the softened butter, peanut butter and 1/4 cup of the powdered sugar until smooth and slightly lightened.
- With the mixer on low, add the remaining powdered sugar 1/4 cup at a time until fully combined and the consistency is right for spreading.
- Stir in the vanilla and salt, then beat on high for 2–3 minutes until the frosting is fluffy and whipped. Spread over the cooled cake and finish with chocolate shavings if desired.
Tips for Frosting
- Regular creamy peanut butter gives the most consistent texture. If you use a different brand, adjust powdered sugar to reach the desired thickness.
- Adding a small amount of powdered sugar at the start helps the butter and peanut butter emulsify smoothly.
- Add powdered sugar gradually to avoid a cloud of sugar and to better control frosting texture.
- If frosting is too thin, add more powdered sugar; if too thick, thin with a splash of milk.
How to Store Peanut Butter Sheet Cake
Store the frosted cake in an airtight container in the refrigerator for 3–4 days. Bring slices to room temperature before serving for the best flavor and texture.
Can You Freeze This Cake?
Yes. The cake freezes well, frosting and all. Freeze uncovered on a baking sheet until firm, then wrap:
- Sliced: wrap individual slices in plastic wrap and place in an airtight container for up to 2 months.
- Unsliced / whole cake: wrap the pan (or the cake) tightly in plastic wrap, then foil, then another layer of plastic for up to 2 months.
Thaw the cake overnight in the fridge. Single slices can come to room temperature in about 30 minutes, depending on your kitchen.
Substitutions and Variations
If you prefer a different topping, try chocolate, caramel or Nutella frostings instead of peanut butter buttercream. Be cautious substituting another nut or seed butter — textures and moisture levels vary and may affect the cake and frosting.
More Peanut Butter Desserts
- Classic Peanut Butter Bars
- Easy Peanut Butter Blossoms
- Peanut Butter Cheesecake Oreo Brownies
- Chocolate Chip Peanut Butter Muffins
- Peanut Butter Mug Cake
- Scotcheroos
- Peanut Butter Icebox Cake
- Instant Pot Peanut Butter Cheesecake
- Peanut Butter Banana Bread
Peanut Butter Sheet Cake
Ingredients
Peanut butter cake:
- 2 cups (9 1/4 oz) all-purpose flour
- 2 teaspoons baking powder
- 1/4 teaspoon salt
- 1/2 cup brown sugar
- 1/2 cup granulated sugar
- 3/4 cup creamy peanut butter
- 1/2 cup vegetable oil
- 2 teaspoons vanilla extract
- 2 large eggs
- 3/4 cup whole milk
Peanut butter frosting:
- 3/4 cup (1 1/2 sticks) unsalted butter, softened
- 3/4 cup creamy peanut butter
- 1 1/2 cups powdered sugar, sifted
- 1 teaspoon vanilla extract
- 1/2 teaspoon salt
- Chocolate shavings, for garnish (optional)
Instructions
Make the peanut butter sheet cake:
- Preheat the oven to 350°F. Grease and line a 9×13-inch baking tin with parchment.
- Whisk the flour, baking powder and salt together in a medium bowl.
- In a large bowl or mixer, beat both sugars, peanut butter, oil and vanilla until combined. Scrape the bowl.
- Add the eggs one at a time, beating well and scraping the sides as needed.
- Add 1/3 of the flour mixture and fold with a spatula. Add half the milk and fold, then repeat (flour, milk, flour) until just combined.
- Spread batter into the prepared pan and bake 18–20 minutes, or until a toothpick shows a few crumbs but no wet batter. Cool completely.
Make the peanut butter frosting:
- Beat the butter, peanut butter and 1/4 cup powdered sugar until smooth and lighter.
- With the mixer on low, add the remaining powdered sugar 1/4 cup at a time until combined.
- Add the vanilla and salt, then beat on high for 2 minutes until fluffy. Spread over the cooled cake and sprinkle chocolate shavings if using.
Recipe Notes
Weighing flour with a kitchen scale yields the most consistent results. If measuring by cup, fluff the flour, spoon it into the cup and level off. This cake stores well for 3–4 days when covered.
Nutrition
Serving: 1 bar • Calories: 258 kcal • Carbohydrates: 28 g • Protein: 6 g • Fat: 15 g • Saturated Fat: 6 g • Sodium: 208 mg