Peanut butter cake with peanut butter frosting is a soft, moist 9×13-inch sheet cake with peanut butter melted right into the batter, covered with a thick, creamy peanut butter frosting. It is sweet, a little salty and deeply nutty, and it stays moist for days. It is an old-fashioned potluck cake, perfect for birthdays, church suppers and anyone who would eat peanut butter straight from the jar.
How to make peanut butter cake with peanut butter frosting: Whisk flour, sugar and baking soda, then beat in milk, eggs and vanilla. Heat water, butter and peanut butter in a saucepan until blended and stir it into the batter. Bake in a greased 9×13-inch dish at 350°F for 35 to 40 minutes. Cool the cake, then spread on a frosting of butter, peanut butter and powdered sugar.
Why You’ll Love It
- Peanut butter twice. In the cake and in the frosting.
- One pan. Baked, frosted and served from the same dish.
- Pantry ingredients. Nothing special to buy.
- An easy frosting. Three ingredients, plus a splash of milk if you need it.
- It serves a crowd. Twelve generous pieces.
Ingredient Notes
Flour, sugar and baking soda. Two cups of flour, 2 cups of sugar and 1 teaspoon of baking soda are the dry base.
Milk, eggs and vanilla. Half a cup of milk, 2 eggs and 1 teaspoon of vanilla go into the batter.
Water, butter and peanut butter. One cup of water, 1/2 cup of butter and 3/4 cup of peanut butter are warmed together on the stove.
Peanut butter. Smooth, shelf-stable peanut butter works best. Runny, oily natural peanut butter can make the cake and frosting greasy.
For the frosting. Half a cup of softened butter, 1 cup of peanut butter, 2 cups of powdered sugar and up to 3 tablespoons of milk for thinning.
Ingredients
For the cake
- 2 cups flour
- 2 cups sugar
- 1 teaspoon baking soda
- 1/2 cup milk
- 2 eggs
- 1 teaspoon vanilla
- 1 cup water
- 1/2 cup butter
- 3/4 cup peanut butter
For the frosting
- 1/2 cup butter, softened
- 1 cup peanut butter
- 3 tablespoons milk, for thinning as needed
- 2 cups powdered sugar
How to Make Peanut Butter Cake with Peanut Butter Frosting
1. Prepare the pan. Preheat the oven to 350°F. Grease a 9×13-inch baking dish with butter and dust it with flour.
2. Mix the cake ingredients. Whisk the flour, sugar and baking soda in a large bowl. Add the milk, eggs and vanilla. Beat on low speed until blended.
3. Heat the peanut butter mixture. In a saucepan over medium heat, stir the water, 1/2 cup butter and 3/4 cup peanut butter frequently until blended, about 5 minutes.
4. Finish the batter. Stir the warm peanut butter mixture into the flour mixture until well mixed. Pour the batter into the prepared dish.
5. Bake and cool. Bake for about 35 to 40 minutes, until a toothpick inserted into the center comes out clean. Allow the cake to cool before frosting.
6. Make the frosting. Cream together the softened 1/2 cup butter and 1 cup peanut butter. Slowly add the powdered sugar. If the frosting gets too thick, add some of the frosting milk to thin it. Continue until the sugar is incorporated and the frosting is blended.
7. Frost the cake. Spread the frosting over the cooled cake.
When Should the Frosting Go On?
After the cake has cooled. This frosting is made by creaming butter and peanut butter, so it is thick and fluffy, like a buttercream. Spread on a warm cake, the butter in it melts, and the frosting turns oily and slides toward the edges of the pan.
It is easy to get this wrong, because another well-known peanut butter cake works the opposite way. The two are built differently.
| This cake | The thin Texas-style sheet cake | |
|---|---|---|
| Pan | 9×13-inch baking dish | 13×18-inch sheet pan |
| Frosting | Creamed butter, peanut butter and powdered sugar | A frosting heated on the stove |
| When it goes on | After the cake cools | While the cake is still warm |
| Result | A thick, fluffy layer | A thin, glossy glaze that sets |
So for the cake on this page, wait. Let the pan sit on a rack until the top no longer feels warm to your hand, then frost.
Tips for Success
How do I thin peanut butter frosting if it gets too thick?
Add a little of the milk, mix, and look again. You have 3 tablespoons to work with, but you may not need it all. Stop when the frosting spreads easily.
Why heat the peanut butter with water and butter?
Warming them together melts the peanut butter into a smooth liquid that blends evenly through the batter. Stir often so it does not catch on the bottom of the pan.
How do I know the cake is done?
A toothpick pushed into the center comes out clean, after about 35 to 40 minutes.
Which peanut butter should I use?
A smooth, shelf-stable one. The oily, natural kind that separates in the jar is harder to work with here.
Do I have to flour the pan?
Butter and flour keep the cake from sticking, which matters when you lift out the first piece.
How Long Does It Take?
About 80 minutes of working time: 45 minutes of prep and about 35 minutes in the oven. The cake also needs time to cool before it is frosted.
Can You Put Peanut Butter in Cake Batter?
Yes. Here, 3/4 cup of peanut butter is melted with water and butter and stirred straight into the batter. It flavors the whole cake and helps keep it moist.
Storage
Cover the pan and keep leftover cake in the refrigerator. Let a piece sit out for a few minutes before eating, so the frosting softens. The cake can also be frozen once it has cooled. Freeze frosted pieces uncovered until firm, then wrap them, so the frosting is not squashed.
What to Serve With It
A cold glass of milk is the classic partner. For more peanut butter desserts, try the slow cooker Amish peanut butter pie, peanut butter crunch lasagna, peanut butter and chocolate Rice Krispie treats or air fryer peanut butter cookies. For other cakes baked in one pan, there are the salted caramel Kentucky butter cake and Bea’s blueberry sheet cake.
Frequently Asked Questions
Should peanut butter frosting go on this cake while it is warm or after it cools?
After it cools. The creamed frosting melts on a warm cake.
Can I put peanut butter in my cake batter?
Yes. This batter has 3/4 cup, melted with water and butter.
How do I thin peanut butter frosting if it gets too thick?
Mix in a little milk at a time, up to 3 tablespoons.
What size pan do I need?
A 9×13-inch baking dish.
Final Notes
I make the frosting while the cake cools, and I add the milk a spoonful at a time, because how much it needs changes with the peanut butter. If you make it, leave a comment to tell me how it turned out or ask a question.
Peanut Butter Cake with Peanut Butter Frosting
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Ingredients
- 2 cups flour for the cake
- 2 cups sugar for the cake
- 1 teaspoon baking soda
- 1/2 cup milk for the cake
- 2 eggs for the cake
- 1 teaspoon vanilla for the cake
- 1 cup water
- 1/2 cup butter for the cake
- 3/4 cup peanut butter for the cake
- 1/2 cup butter softened, for the frosting
- 1 cup peanut butter for the frosting
- 3 tablespoons milk for thinning the frosting as needed
- 2 cups powdered sugar for the frosting
Instructions
- Preheat the oven to 350°F. Grease a 9x13-inch baking dish with butter and dust it with flour.
- Whisk the flour, sugar and baking soda in a large bowl. Add the milk, eggs and vanilla. Beat on low speed until blended.
- In a saucepan over medium heat, stir the water, 1/2 cup butter and 3/4 cup peanut butter frequently until blended, about 5 minutes.
- Stir the warm peanut butter mixture into the flour mixture until well mixed. Pour the batter into the prepared dish.
- Bake for about 35 to 40 minutes, until a toothpick inserted into the center comes out clean. Allow the cake to cool before frosting.
- Cream together the softened 1/2 cup butter and 1 cup peanut butter. Slowly add the powdered sugar. If the frosting gets too thick, add some of the frosting milk to thin it. Continue until the sugar is incorporated and the frosting is blended.
- Spread the frosting over the cooled cake.
