Mom's Best Recipes
Recipe

Peanut Butter Cake With Fluffy Frosting

A tender, old-school peanut butter cake baked in a 9x13 and topped with a creamy peanut butter frosting that tastes like the inside of a peanut butter cup.

Author By Matt Campbell
4.8
A thick slice of peanut butter sheet cake on a plate with a generous layer of creamy peanut butter frosting, soft crumbs visible, on a warm kitchen table with natural light
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If you want a cake that feels like a hug but still has a little attitude, peanut butter cake is it. It is sweet, yes, but also toasty and nutty and weirdly nostalgic in the best way. This version bakes up plush and tender in a simple 9x13 pan, then gets topped with a fluffy peanut butter frosting that makes you do that mid-bite pause like, okay wow.

No hard-to-find ingredients, no fancy layers, no stress. Just a dependable cake you can bring to a school event, a potluck, or your own kitchen counter at 9:30 pm when you are craving something cozy and unapologetically peanut buttery.

Measured baking ingredients for peanut butter cake including flour, sugar, brown sugar, peanut butter, eggs, buttermilk, and butter arranged on a kitchen counter with warm light

Why It Works

  • Big peanut butter flavor without dryness: Creamy peanut butter plus buttermilk keeps the crumb tender and moist.
  • One pan, low drama: A 9x13 sheet cake means easy baking, easy frosting, easy serving.
  • Frosting that behaves: Whipped peanut butter frosting spreads smoothly and sets just enough so slices look clean.
  • Flexible sweetness: You can dial it up with chocolate chips or keep it classic with a sprinkle of flaky salt.

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Storage Tips

Room temperature: Store the frosted cake tightly covered for up to 2 days. If your kitchen is warm or humid, refrigerate sooner.

Refrigerator: Cover and refrigerate up to 5 days. For the best texture, let slices sit at room temp for 20 to 30 minutes before eating so the frosting softens.

Freezer: Freeze individual slices for up to 2 months. Wrap each slice in plastic wrap, then foil. Thaw overnight in the fridge or for about an hour on the counter.

Common Questions

Can I use natural peanut butter?

You can, but it is less predictable. Natural peanut butter can separate and throw off the texture, making the cake or frosting a bit oily or grainy. If you want to try it anyway, stir it extremely well (and pour off any excess oil if there is a lot), then chill the frosting for 15 to 20 minutes if it feels loose.

What if I do not have buttermilk?

Make a quick substitute: add 1 tablespoon lemon juice or white vinegar to a measuring cup, then fill to 1 cup with milk. Stir and let sit 5 minutes before using.

Can I make this as a layer cake?

Yes. Bake in two 8-inch round pans for 24 to 28 minutes, or until a toothpick comes out with a few moist crumbs. Cool completely before frosting.

How do I keep the cake from sticking?

For a 9x13, I like parchment plus grease: lightly grease the pan so the parchment sticks, lay in a parchment sling, then grease the parchment. It is the easiest way to lift and slice clean squares.

Can I add chocolate?

Absolutely. Stir 1 cup mini chocolate chips into the batter, or drizzle the frosted cake with 1/2 cup melted chocolate (or a simple ganache made from 1/2 cup chocolate chips + 1/4 cup hot cream, stirred until smooth). Peanut butter and chocolate are best friends who never fight.

Any allergy notes?

This cake contains peanuts, dairy, eggs, and wheat.

I love ambitious cooking projects, but cake is where I want the opposite energy. I want something that feels like it has always existed, like you could set it down at a family gathering and nobody would ask questions. Peanut butter cake is exactly that. It is the bake I reach for when I want guaranteed smiles and a little kitchen chaos in the form of frosting swirls. Also, I fully support cutting the first slice while it is still slightly warm and calling it “quality control.”