Sheet Pan Peanut Butter Cake

2 Pieces of Peanut Butter Cake on Plate Close Up
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One of my all-time favorite potluck desserts is Sheet Pan Peanut Butter Cake! This peanut butter cake recipe is ultra-moist and is covered in sweet, fudgy frosting. I love to take this cake to family reunions, picnics, and birthday celebrations. This cake is filling and rich enough to feed about 20 people. It is beloved by adults and kids alike, and it always disappears before I get a chance for seconds.

If you love peanut butter, and peanut butter fudge, this cake is exactly what you are looking for. We love to serve it up with a big scoop of vanilla ice cream if we are indoors for a birthday. You won’t find a better Sheet Pan Peanut Butter Cake than this one.

The Peanut Butter Cake

To begin, grease a 10×15 cookie sheet with non-stick cooking spray. I actually used an 11×17, but the 10×15 would be even better. Preheat your oven to 350 degrees.

Whisk together the flour, granulated sugar, baking soda, and kosher salt. Set aside for later.

Bowl with Dry Ingredients

Melt margarine in a medium pot over medium-low heat. Add 1 cup of water, raise heat, and bring to a boil for 1-2 minutes.

Boiling Margarine and Water in Sauce Pan

Turn burner off and whisk in 1/2 cup peanut butter.

Sheet-Pan-Peanut-Butter-Cake Peanut Butter in Pan with Water, Margarine

Move the pan off the warm burner. Next, whisk in the dry ingredients.

Whisking in Dry Ingredients

The batter should be starting to form at this stage, but we have a few more wet ingredients yet.

Sheet-Pan-Peanut-Butter-Cake after whisking in Dry Ingredients

This recipe calls for sour milk. To make your milk sour, just stir 1 tsp of white vinegar into 1 cup of milk. Add the sour milk, 2 eggs, and vanilla to the pot and whisk just until smooth.

Whisking in Eggs, Milk, Vanilla

The batter should look like the picture below:

Cake Batter Fully Mixed

The batter should still be warm, and easily pour-able into the greased cookie sheet. Pour as evenly as you can, and give the pan a gently tap on the counter to release any air bubbles.

Cake Batter Being Poured into Baking Sheet

Bake at 350 degrees for 20-25 minutes. Meanwhile, get the frosting started while the cake is baking.

The Peanut Butter Frosting

For the frosting, melt margarine over low-medium heat in a large sauce pan or medium pot. Stir in the peanut butter.

Margarine Melting in Pan

Add powdered sugar, vanilla, salt, and 4 Tbsp milk. Carefully whisk the ingredients together until a smooth frosting forms. Maybe go for the medium pot instead of the sauce pan, so you don’t make a mess like me, haha!

Powdered Sugar with Butter and Peanut Butter for Frosting

The frosting will be a pretty beige color, and should be somewhat thin and pour-able so it will glaze the hot cake. Add 1-2 Tbsp more milk, as needed to get the pour-able frosting consistency .

Finished Frosting in Pan

By now, the cake should be finished baking. Insert a toothpick into the center to check for done-ness. It will come back clean when the cake is finished baking.

Place a large piece of parchment paper on your counter, then place the cake on top of a trivet centered over the parchment paper.

Sheet Pan Peanut Butter Cake Fresh From the Oven

Now it is time for the tricky part, pouring the frosting on the hot cake.

As you can see, the frosting has an almost ribbon-like quality as it coats the hot cake. There is a chance of making a mess with this step, so just work carefully to pour the frosting in the center and gently spread to the edges with a spatula, as needed

Peaut Butter Frosting being poured over peanut butter cake

Let the frosting set for about 30 minutes. Serve, and enjoy! The Sheet Pan Peanut Butter Cake will stay fresh for up to 4 days on your counter, if covered with foil or cling-wrap.

2 Pieces of Peanut Butter cake on a plate
2 Pieces of peanut butter cake on a plate

Sheet Pan Peanut Butter Cake

Ultra-moist peanut butter cake with fudgy peanut butter frosting
Cook Time 35 mins
Total Time 1 hr 5 mins
Course Dessert
Cuisine American
Servings 20

Ingredients
  

Peanut Butter Cake

  • 1 cup Margarine/Oleo (2 sticks)
  • 1 cup Water
  • 1/2 cup Smooth Peanut Butter
  • 2 cups All Purpose Flour
  • 2 cups Granulated Sugar
  • 2 meduim Eggs
  • 1/2 cup Milk (2% or Vitamin D)
  • 1 tsp White Vinegar
  • 1 tsp Vanilla Extract
  • 1 tsp Baking Soda
  • 1/2 tsp Kosher Salt

Peanut Butter Frosting

  • 1/2 cup Oleo/Margarine
  • 1/2 cup Peanut Butter
  • 4 cups Powdered Sugar
  • 1 tsp Vanilla Extract
  • 1 pinch Kosher Salt
  • 4-5 Tbsp Milk (2% or Vitamin D)

Instructions
 

Peanut Butter Cake

  • Preheat oven to 350 degrees. Spray a 10×15 cookie sheet with non-stick cooking spray.
  • Melt margarine in a medium pot over medium-low heat. Once melted, add 1 cup water, and increase heat and bring mixture to a boil for about 1-2 minutes. Turn burner off, and whisk in 1/2 cup peanut butter. Set aside.
  • Whisk together flour, granulated sugar, baking soda, and kosher salt. Whisk flour mixture into the peanut butter mixture in pot from previous step.
  • Stir 1 teaspoon white vinegar into 1 cup milk.
    Next, whisk into the medium pot, the eggs, sour milk, and vanilla, just until smooth.
  • Pour cake batter into greased cookie sheet. Bake for 20-25 minutes, or until a tester toothpick inserted into the cake comes out clean.

Peanut Butter Frosting

  • While cake is baking, make the frosting.
  • Melt and whisk together 1/2 cup margarine and 1/2 cup peanut butter over low heat. Keep heat on very low, and add powdered sugar, vanilla, and a pinch of kosher salt. Add 4 Tbsp of Milk and whisk the frosting together.
    Add 1 or 2 more Tbsp of Milk, as needed for the frosting to have a slightly thin, pourable consistency.
  • When the cake is finished baking, place the sheet pan on a trivet on top of a large piece of parchment paper. Pour the frosting over the hot cake, being careful not to let it run off the sides if you can help it.
  • Let the frosting set for about 30 minutes. Serve, and enjoy!
Keyword Moist cake, Peanut Butter Cake, Peanut Butter Dessert, Sheet Pan Peanut Butter Cake

Like this recipe? Try my Bakery Style Blueberry Muffins!

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