
This rich peanut butter cake has become my signature dessert for birthdays and celebrations, combining the beloved flavors of creamy peanut butter with colorful M&M's for a treat that's as beautiful as it is delicious.
I first made this cake for my nephew's fifth birthday when I was in a pinch for time. The combination of peanut butter and candy was such a hit that it's now requested at nearly every family gathering we have.
Ingredients
- All purpose flour: creates the perfect cake structure without being too dense
- Baking powder and baking soda: work together for the ideal rise and texture
- Unsalted butter: adds richness while letting you control the salt content
- Creamy peanut butter: is the star ingredient choose a high quality brand for best flavor
- Granulated sugar: sweetens while helping create a tender crumb
- Large eggs: provide structure and moisture
- Vanilla extract: enhances all the flavors without overwhelming
- Buttermilk: makes the cake incredibly tender and adds subtle tanginess
- Colorful M&Ms: bring fun pops of color and crunchy texture throughout
- Powdered sugar: creates silky smooth frosting without graininess
- Heavy cream: gives the frosting an irresistible lightness
Step-by-Step Instructions
- Prepare Your Space:
- Heat your oven to exactly 350°F and prepare your cake pans by thoroughly greasing and flouring them. This preparation step is crucial for clean removal later. Take time to ensure even coverage in all corners of the pans.
- Create Your Dry Mix:
- Whisk the flour, baking powder, baking soda, and salt in a medium bowl until completely combined. This thorough mixing ensures the leavening agents are distributed evenly throughout the batter, preventing uneven rising.
- Start The Batter Base:
- Beat room temperature butter and peanut butter together for a full 3 minutes until the mixture becomes notably lighter in color and creamy in texture. The butter must be truly room temperature not just slightly softened for proper incorporation.
- Build The Wet Mixture:
- Add sugar gradually while continuing to beat until the mixture becomes fluffy and aerated, about 2 more minutes. Then incorporate eggs one at a time, allowing each to fully integrate before adding the next. This patience prevents curdling. Finally, mix in vanilla to distribute the flavor evenly.
- Combine Wet And Dry:
- Add the dry ingredients in three portions, alternating with buttermilk in two portions, always beginning and ending with dry ingredients. Mix gently just until combined after each addition. Overmixing at this stage will develop gluten and create a tough cake.
- Add Candy:
- Gently fold in M&Ms using a spatula with a light hand to prevent breaking the candies or deflating your batter. The goal is even distribution throughout without overworking the batter.
- Bake To Perfection:
- Divide batter evenly between prepared pans, using a kitchen scale if available for precision. Bake in the middle rack of your preheated oven for 25 to 30 minutes. Start checking at the 25 minute mark by inserting a toothpick in the center it should come out with a few moist crumbs but no wet batter.
- Cool Strategically:
- Allow cakes to cool in pans for exactly 10 minutes no more, no less. This timing allows the cakes to set while still being loose enough to remove cleanly. Transfer to cooling racks and let them cool completely before frosting, at least 1 hour.
- Prepare Frosting:
- Beat butter and peanut butter together for 2 full minutes until extremely creamy and uniform in color. The butter must be completely soft for a smooth frosting texture.
- Finish Frosting:
- Add powdered sugar one half cup at a time, beating thoroughly between additions. Once all sugar is incorporated, add heavy cream and vanilla, then beat on high speed for 3 full minutes until the frosting becomes remarkably light and fluffy.
- Assemble Layer Cake:
- Place one cake layer on your serving plate and spread a generous 1/2 inch layer of frosting on top, taking care to create an even surface. Position the second layer precisely on top of the first.
- Decorate Beautifully:
- Frost the top and sides of the cake with smooth, even strokes. For the most attractive finish, use an offset spatula to create swirls or patterns in the frosting. Finish by arranging additional M&Ms on top in a decorative pattern or border.

The quality of peanut butter truly makes a difference in this recipe. I once tried using a natural, oil separated peanut butter and the texture was completely different. Stick with traditional creamy peanut butter for the best results every time.
Storage Solutions
This peanut butter cake maintains its moisture remarkably well compared to other cakes. Store it in an airtight container at room temperature for up to three days without any noticeable quality decline. For longer storage, you can refrigerate the cake for up to a week, but always bring it to room temperature before serving to restore the ideal texture and flavor intensity.
If you need to make this cake well in advance, you can freeze the unfrosted cake layers wrapped tightly in plastic wrap and aluminum foil for up to three months. Thaw overnight in the refrigerator before frosting and decorating.
Smart Substitutions
While this recipe is perfect as written, there are several adaptations you can make based on dietary needs or preference. For a nuttier flavor profile, substitute half the all purpose flour with whole wheat flour. If buttermilk isn’t available, use regular milk with a tablespoon of lemon juice or white vinegar stirred in and left to sit for 5 minutes.
For those with peanut allergies, sunflower seed butter makes an excellent alternative with a similar texture and mild flavor. The frosting can be made with less sugar if you prefer a less sweet cake just reduce the powdered sugar to 1 1/2 cups instead of 2.
Serving Suggestions
This peanut butter cake pairs beautifully with a scoop of vanilla ice cream or a glass of cold milk. For an even more decadent dessert experience, try warming individual slices for 10 seconds in the microwave and drizzling with warm chocolate sauce.
When serving at parties, cut smaller slices as this cake is quite rich. I like to prepare some extra frosting on the side for those who enjoy an additional dollop. For a special presentation, add a sprinkle of chopped peanuts around the edge of the serving plate to hint at the flavors inside.

Frequently Asked Questions
- → Can I use natural peanut butter for this cake?
Yes, natural peanut butter can be used, but ensure it’s well-stirred and smooth to prevent texture issues in the batter and frosting.
- → What is the best way to decorate the cake with M&M’s?
Scatter M&M’s evenly on the top for a colorful presentation, or create patterns or designs to customize the decoration.
- → Can I make this cake ahead of time?
Yes, you can bake the cake layers a day in advance. Store them tightly wrapped at room temperature and frost just before serving.
- → What substitutes can I use for buttermilk?
If you don’t have buttermilk, you can mix 1/2 cup of milk with 1/2 tablespoon of lemon juice or vinegar as a substitute.
- → Can I use a different candy instead of M&M’s?
Absolutely! Alternatives like Reese’s Pieces or chocolate chips work well for a different flavor profile.