Peanut Butter Sheet Cake with Peanut Butter Frosting

Peanut Butter Sheet Cake with Peanut Butter Frosting is one of those rich, old-fashioned desserts that I love pulling out for potlucks, birthdays, or just when I want a sweet treat that makes everyone smile. The cake is soft, moist, and full of peanut butter flavor, and the warm, pourable frosting takes it over the top. It’s comforting, easy to make, and always a hit.

Why You’ll Love This Recipe

I love how this cake comes together in one pan with no complicated steps or fancy techniques. The texture is dense yet tender, and the flavor is pure peanut butter bliss. The frosting is my favorite part—smooth, sweet, and poured over the cake while still warm so it sinks in a little and sets to a perfect finish. It’s nostalgic, satisfying, and crowd-friendly.

ingredients

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

For the cake:

• All-purpose flour

• Granulated sugar

• Baking soda

• Salt

• Unsalted butter

• Creamy peanut butter

• Water

• Eggs

• Sour cream or buttermilk

• Vanilla extract

For the frosting:

• Unsalted butter

• Creamy peanut butter

• Milk

• Powdered sugar

• Vanilla extract

directions

1. I preheat the oven to 350°F (175°C) and grease a 9×13-inch baking pan.

2. In a large bowl, I whisk together the flour, sugar, baking soda, and salt.

3. In a saucepan, I melt the butter, peanut butter, and water together over medium heat until smooth, then pour it into the dry ingredients and stir to combine.

4. I mix in the eggs, sour cream, and vanilla until the batter is smooth and well blended.

5. I pour the batter into the prepared pan and bake for 25–30 minutes, or until a toothpick comes out clean.

6. While the cake bakes, I make the frosting: I melt the butter, peanut butter, and milk in a saucepan, then remove it from the heat and stir in powdered sugar and vanilla until smooth.

7. I pour the warm frosting over the hot cake and spread it evenly. I let it set before slicing and serving.

Servings and timing

This sheet cake makes about 16–20 servings, depending on how I slice it. It takes around 15 minutes to prep, 25–30 minutes to bake, and another 10 minutes for frosting and cooling.

Variations

Sometimes I add chopped roasted peanuts on top for extra crunch. I’ve also swirled in chocolate chips or drizzled melted chocolate over the frosting for a peanut butter cup vibe. If I want it less sweet, I reduce the powdered sugar slightly in the frosting.

storage/reheating

I store leftovers covered at room temperature for up to 3 days or in the fridge for up to 5 days. If I want to warm a slice, I microwave it for about 10 seconds—it softens the cake and makes the frosting a little melty and extra delicious.

FAQs

Can I use chunky peanut butter?

Yes, I’ve used chunky peanut butter for extra texture. It adds little bits of peanut throughout, which I really enjoy.

Can I make this cake ahead of time?

Absolutely. I often bake the cake a day in advance and frost it just before serving, or make the entire cake the night before and let it sit at room temperature.

Can I freeze this cake?

Yes, I freeze the cake (frosted or unfrosted) in a well-wrapped container. It thaws beautifully at room temperature.

What can I use instead of sour cream?

I use buttermilk or plain Greek yogurt as a substitute. Both work well and keep the cake moist.

How thick is the frosting?

It’s pourable and smooth while warm but sets into a thick, slightly firm layer as it cools—just the way I like it on a sheet cake.

Conclusion

Peanut Butter Sheet Cake with Peanut Butter Frosting is one of those timeless desserts I always come back to. It’s easy to make, full of flavor, and feeds a crowd with no fuss. Whether I’m baking for a gathering or just treating myself, this cake delivers that classic peanut butter taste I can’t get enough of.