This peanut butter sheet cake with peanut butter icing is the ultimate dessert recipe for potlucks, holidays, barbecues or just for an easy dessert recipe on the weekends.

Peanut butter sheet cake in baking pan, with a couple of pieces removed.

Sheet cakes are probably my favorite type of cake recipes because they’re so easy to make, instead of having to worry about stacking a layered cake, or frosting a round cake.

This depression cake recipe is such a favorite around here, so I knew you’d also love this peanut butter sheet cake too.

Slice of peanut butter cake on a round plate.

Ingredients Needed:

I’ve provided some notes below about some of the key ingredients. The full recipe with a list of the ingredients and amounts can be found in the recipe card below.

Ingredients in bowls that are used for making peanut butter cake with peanut butter icing.

Kosher salt – A little salt brings out the peanut butter flavor and keeps it from tasting flat.
Unsalted butter – For richness and that classic buttery base. Salted works in a pinch—just skip the added salt.
Creamy peanut butter – I use regular store-bought (like Jif or Skippy). Natural peanut butter will make the texture weird unless stirred very well.
Buttermilk – Keeps the cake soft and moist. You can make your own: ½ cup milk + ½ tablespoon vinegar or lemon juice.
Heavy whipping cream – Adds richness and makes the frosting extra smooth and fluffy. You can use whole milk or half and half if you want a thinner consistency.

How to Make Peanut Butter Sheet Cake

Preheat your oven to 350°F. Prepare a 9 x 13-inch baking dish with nonstick cooking spray. Set it aside.

Two images, with left image showing dry ingredients, and right image showing wet.

Whisk together 2 cups all-purpose flour, 2 ¼ cups granulated sugar, 1 teaspoon baking soda, and ½ teaspoon kosher salt in a large mixing bowl.
Combine 1 cup purified water, ½ cup (1 stick) unsalted butter, and ¾ cup creamy peanut butter in a medium saucepan over medium heat. Stir constantly until it comes to a gentle boil and everything is melted and smooth. Remove from heat.

Peanut butter mixture mixed with dry ingredients in left image and then peanut butter cake batter poured in pan.

Pour the warm peanut butter mixture over the dry ingredients and stir until mostly combined. Add ½ cup buttermilk, 2 large eggs, and 2 teaspoons pure vanilla extract, and mix until smooth. Don’t overmix.
Pour the batter into your prepared pan and smooth it out evenly. Bake for 25 to 35 minutes, or until the center is set and a toothpick comes out clean.

Peanut butter cake baked in 9x13 baking pan.

Once the cake is fully baked, remove it from the oven and let it cool completely in the pan on a wire cooling rack—this will take up to 1½ to 2 hours at room temperature. Don’t rush it! If the cake is even a little warm, the frosting will slide right off.

How to Make Peanut Butter Icing

Two images showing how to make peanut butter frosting to go on peanut butter cake.

About 15 to 20 minutes before you’re ready to frost, prepare the buttercream. In a large bowl, beat 1 cup (2 sticks) softened unsalted butter and 1 cup creamy peanut butter together with a hand mixer or stand mixer until light and fluffy—about 2 to 3 minutes.
Add 2 teaspoons pure vanilla extract and a pinch of salt, then mix in 4 cups powdered sugar, one cup at a time. Add ¼ cup heavy cream gradually, beating until the frosting is thick, smooth, and spreadable. Add more heavy cream if needed to thin the frosting or add more powdered sugar if needed to thicken.
Once the cake is completely cool, use an offset spatula to generously spread the peanut butter frosting evenly across the top. If you like a thicker layer, pile it on—you’ve got plenty!

Peanut butter sheet cake, frosting with peanut butter frosting.

More Peanut Butter Cake Topping Ideas

For extra flair, top with chopped roasted peanuts, mini peanut butter cups, or even a drizzle of chocolate.

Recipe Tips

Don’t skip the buttermilk – it keeps the cake soft and tender with just the right balance of tang and richness.
Type of baking pan – If you’re baking this in a glass 9×13 dish, keep in mind that glass retains heat more than metal. Your cake may take an extra 3–5 minutes to bake through. Start checking around the 25-minute mark, but don’t be surprised if it needs closer to 35 minutes. A metal pan will give you slightly crisper edges, while glass tends to produce a softer, more even bake.
Pipe the frosting on the cake first, then use an offset spatula to smooth out the frosting.

Slice of peanut butter cake, with a bite taken out of it.

How to Store Leftover Cake

Store any leftovers covered at room temperature for up to 3 days or in the fridge for up to 5 days. Once cooled, cover the sheet cake tightly with foil or plastic wrap and store at room temperature for up to 3 days.
You can refrigerate it for up to 5 days, but bring it to room temperature before serving for the best texture.
To make ahead, bake the cake a day in advance and store it covered. Make the frosting fresh and pour it on the next day to wow your guests with that fresh, glossy finish.

If you love peanut butter desserts like this one, you’ll also love these:

Did you make this? I’d be so grateful if you left a “star” rating below to let me know what you thought! Then, the next time you need a quick and easy recipe, come back to Fantabulosity to browse all of my easy recipes!