Cake Mix Peanut Butter Cake

I baked an easy yet indulgent peanut butter cake using a boxed cake mix, creamy peanut butter, butter, eggs, and water—topped with a rich peanut butter frosting. It’s soft, flavorful, and comes together quickly!

Why You’ll Love This Recipe

I adore this recipe because it’s a double dose of peanut butter—infused in both the cake and the frosting. It’s simple, requires minimal ingredients, and gives me a moist, crowd-pleasing cake without fuss.

Ingredients

(Here’s a tip: Check out the full list of ingredients and measurements in the recipe card below.)

• ½ cup creamy peanut butter

• ½ cup butter, softened

• 4 large eggs

• 1 (15.25-oz) box butter or yellow cake mix

• ⅔ cup water

For the frosting:

• 1 cup peanut butter

• ½ cup butter, softened

• 4 cups powdered sugar

• ⅓ cup heavy cream

Directions

1. Preheat oven to 325°F. Grease and flour two 9-inch round cake pans.

2. Beat ½ cup peanut butter and ½ cup butter until light and fluffy. Add eggs one at a time, mixing well.

3. Add cake mix alternately with water; stir until just combined.

4. Divide batter between pans and bake for 25 minutes, or until a toothpick comes out clean. Cool in pans for 10 minutes, then transfer to wire racks to cool completely.

5. For the frosting, beat 1 cup peanut butter and ½ cup butter until creamy. Add powdered sugar, mixing until smooth. Beat in heavy cream until spreadable.

6. Fill and frost the cooled cake layers.

Servings and timing

This recipe makes a two-layer 9-inch cake, serving about 12 slices.

• Prep time: ~30 minutes

• Bake time: ~25 minutes

• Cooling & assembly: ~10 minutes + frosting

• Total time: ~1 hour 5 minutes

Variations

• I sometimes swap water for milk or use vegetable oil for added richness.

• I like switching between yellow, white, or butter cake mix depending on what flavor I want.

• For extra texture and sweetness, I top the cake with chopped peanut butter cups or use a chocolate frosting instead.

Storage/reheating

I store any leftovers covered in the refrigerator for up to 3 days. Slices freeze well for up to 2 months if wrapped tightly. When ready to eat, I thaw them at room temperature or warm gently in the microwave.

FAQs

How can I make this recipe gluten-free?

I swap the cake mix for a gluten-free version—most blends work the same, though baking time might vary slightly.

Can I use natural peanut butter?

I prefer processed, no-stir peanut butter because natural kinds can make the cake and frosting oily.

How do I make cupcakes instead?

I fill cupcake liners two-thirds full and bake at 350°F for about 18 minutes. I check them around the 15-minute mark.

Can I make this a sheet cake?

Yes—I bake it in a greased 9×13 pan for about 30 to 35 minutes and then frost it once cooled.

Can I use milk instead of heavy cream in the frosting?

Yes—milk works just fine. The texture might be slightly thinner, but I still get great results.

Conclusion

I love how this semi-homemade cake delivers big flavor with little effort. With pantry staples and a boxed mix, I get a decadent, moist peanut butter cake perfect for birthdays, potlucks, or just a cozy dessert at home.

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