This easy peanut butter cake is made in one bowl using pantry staples. It comes together quickly and delivers deep peanut butter flavor with a creamy, irresistible frosting.
If you love peanut butter, this cake might become your new go-to dessert. A doctored cake mix creates a tender, moist base that’s finished with a rich, creamy peanut butter frosting. It’s simple enough for a weeknight bake but impressive enough for gatherings.
Why you’ll love this easy peanut butter cake:
- Made with common pantry ingredients.
- Prepared in one bowl—no stand mixer required.
- Holds up well in the fridge, so you can make it ahead.
How to make the cake
- Combine the cake mix, water, peanut butter, oil, eggs, and vanilla in a large bowl.
- Beat with an electric mixer until smooth and uniform, scraping the bowl as needed.
- Pour the batter into a prepared 13-by-9-inch pan and bake until a tester comes out clean.
Bake time is typically about 30–35 minutes. Let the cake cool completely on a wire rack before you frost it.
Tip: I used a yellow cake mix in this version, but a white cake mix works well if you prefer a lighter crumb.
How to make the frosting
- Warm peanut butter, butter, and milk in a saucepan over medium heat, stirring until smooth and melted.
- Remove from heat and whisk in powdered sugar, vanilla, and a pinch of salt until smooth. The frosting will be pourable but thick.
- Pour the frosting over the cooled cake and spread gently. Sprinkle chopped salted peanuts on top if desired.
The frosting is creamier and softer than a traditional buttercream. It firms up in the refrigerator but remains silky, which many find delightful.
Serving ideas: Top with roasted salted peanuts, chopped peanut butter cups, chopped candy bars, or candy pieces for extra texture and flavor.
How to store the cake
After frosting, keep the cake covered in the refrigerator for up to two days. Individual slices freeze well—wrap tightly and freeze for up to two months. An unfrosted cake can sit covered at room temperature for about a day before you frost it.
Substitutions and variations
Use a processed creamy peanut butter (not natural) so the texture and consistency remain stable in both cake and frosting. If you want to make this recipe into layers or cupcakes:
- For a two-layer 8-inch cake: bake in two 8-inch pans. Start checking for doneness at about 25 minutes to avoid overbaking.
- For cupcakes: fill 24–28 muffin cups and begin checking for doneness at 18 minutes.
- Note: the poured frosting in this recipe is best for sheet cakes. For layer cakes or cupcakes, consider a firmer peanut butter buttercream.
Other peanut butter treats you might enjoy:
- White Chocolate Peanut Butter Balls
- 3-Ingredient Peanut Butter Fudge
- Praline Cake
- Peanut Butter Cupcakes
Did you make this easy peanut butter cake? Leave a comment with your feedback and a rating. Share your photo on social media and tag @theitsybitsykitchen so the author can see your version.
Easy Peanut Butter Cake
Prep time: 20 mins — Cook time: 30 mins — Cooling time: 3 hrs — Total time: 50 mins
Summary: A quick doctored cake mix creates a moist peanut butter cake finished with a silky peanut butter frosting. Perfect for peanut butter lovers.
Ingredients
Peanut Butter Cake
- 1 (15.25-ounce) box yellow cake mix*
- 1 1/4 cups water
- 1/2 cup creamy peanut butter (not natural)
- 1/3 cup vegetable oil
- 4 large eggs
- 1 teaspoon vanilla extract
Peanut Butter Frosting
- 2/3 cup creamy peanut butter (not natural)
- 1/2 cup unsalted butter
- 1/2 cup whole milk
- 3 1/2 cups powdered sugar
- 1/2 teaspoon vanilla extract
- 1/4 teaspoon salt
- Salted peanuts, coarsely chopped, for serving (optional)
Instructions
- Preheat oven to 350°F (175°C). Spray a 13-by-9-inch baking dish with cooking spray and set aside.
- In a large mixing bowl, combine the cake mix, water, peanut butter, vegetable oil, eggs, and vanilla. Beat with an electric mixer on medium for about 2 minutes, until smooth. Scrape the sides and bottom of the bowl and beat briefly more.
- Pour the batter into the prepared pan and bake 30 to 35 minutes, or until a tester inserted into the center comes out clean. Cool completely on a wire rack before frosting.
- For the frosting: in a medium saucepan over medium heat, combine peanut butter, butter, and milk. Stir often until melted and smooth. Remove from heat and whisk in powdered sugar, vanilla, and salt until the mixture is thick but still pourable.
- Pour the frosting over the cooled cake and smooth the top. Sprinkle with chopped peanuts if desired. Refrigerate 20 to 30 minutes to set the frosting, then slice and serve.
- Store leftovers covered in the refrigerator for up to 2 days, or wrap slices tightly and freeze for up to 2 months.
Notes
- *I used a yellow cake mix; a white cake mix is an acceptable substitute.
- Before frosting, an unfrosted cake can be stored covered at room temperature for about a day.
- Alternative toppings include chopped peanut butter cups, chopped candy bars, or candy pieces.
- For layer cakes or cupcakes, consider using a stiffer peanut butter buttercream instead of this poured frosting.