Peanut Butter Cake with Marshmallow Frosting

Rich peanut butter cake topped with glossy homemade marshmallow frosting is pure decadence and the perfect addition to any celebration

I was in fifth grade when I had my first fluffernutter sandwich. We were out of jelly and being that all I knew how to make for lunch back then was a peanut butter and jelly I was in crisis mode. That’s when my dad stepped in and suggested using marshmallow fluff as a sub for jelly and – oh my – so, so good.

So in honor of his heroism all those years ago, I made for him a peanut butter cake with marshmallow frosting; i.e., a fluffernutter cake.


We celebrated his birthday a couple weeks ago with grilled t-bone steak lunch and finished the meal with this cake. Because birthdays should always be concluded with cake.

I used all purpose flour for the cake. Compared to cake flour it creates a more dense cake which I think works well with the peanut butter. Brown sugar also lends a hand to create the perfect texture. This cake is rich, but not too dense and has the perfect amount of peanut butter.


You might recognize the frosting recipe as the filling for these whoopie pies. It’s light, airy, and adds the right amount of sweetness. It won’t hold up for more than a day or two so I recommend making the frosting and decorating the cake the same day you plan on serving it. The cake, however, can be made in advance. If you plan on making it more than a day early, you can wrap each layer in in plastic wrap and pop it in the freezer for a week. Just be sure to allow it to thaw completely before frosting.


This cake is good and the perfect treat for any fluffernutter lover. Make it for your next celebration!

Peanut Butter Cake with Marshmallow Frosting

  • 2 1/4 All-Purpose Flour
  • 2 Tsp Baking Powder
  • 3/4 Tsp Salt
  • 1/2 Cup Unsalted Butter, Softened
  • 1/2 Cup Peanut Butter
  • 3/4 Cup Granulated Sugar
  • 3/4 Cup Brown Sugar
  • 2 Eggs
  • 2/3 Cup Buttermilk
  • 2 Tsp Vanilla Extract
  • Peanuts (Optional)

Preheat the oven to 350. Grease 2 9 inch round cake pans and line the bottoms with a sheet of parchment paper.

Sift the flour, baking powder, and salt together and set aside. Combine the butter, peanut butter, and sugars in a mixing bowl and beat on high for about 3 minutes, until light and fluffy. Turn the mixer to medium and add the eggs one at a time. Drizzle in the buttermilk and vanilla extract. Slowly add in the dry ingredients and mix until just combined.

Pour the batter into the prepared pans and bake for 20-25 minutes until a toothpick inserted into the center comes out clean. Allow to cool for 10 minutes before removing from the pans. Allow to cool before frosting with marshmallow frosting (instructions below). Garnish with peanuts (optional).

For the Marshmallow Frosting

  • 1 Cup of Sugar
  • 1/4 Cup of Water
  • 2 Egg Whites (1/2 a cup of egg whites)
  • 2 Tsp Corn Syrup
  • 1 Tsp Vanilla
  • 1/4 Tsp Salt

Fill a medium sized with about an inch of water and bring the water to a simmer over medium high heat. Place your mixing bowl over the pan and whisk together the sugar, water, egg whites, and corn syrup in the double border. Continue to whisk until the temperature reaches 140.

Remove from the heat and add the vanilla and salt. If using a stand mixer, use the wire whisk attachment. Beat the mixture on high until it’s fluffy and glossy. This may take 10 minutes.