Peanut Butter Cake has a moist, light, and airy crumb. It's paired with a creamy, fluffy homemade peanut butter frosting that tastes incredibly similar to a Nutter-Butter cookie. Seriously, this is the best gluten free peanut butter cake recipe.

It's even been Finn approved (my dog). To be completely honest, I set out to develop a peanut butter cake recipe for my dog's 2nd birthday. Prior to this momentous event, we hadn't ever had a peanut butter cake or really even heard of one.

If you're a peanut butter fiend, this one's for you.

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What Makes Peanut Butter Cake So Good?

High-quality gluten-free all purpose flour containing xanthan gum. This recipe uses rice-based flour as its gluten-free base. I use Bob's Red Mill 1:1 Gluten Free Baking Flour (the blue bag). If you don't need to eat gluten-free, this recipe should work by subbing equal parts regular all-purpose flour.
Creamy peanut butter. Since both the cake and icing rely heavily upon peanut butter in this recipe, you must pick the right kind. You want creamy peanut butter that is not oily - no completely natural peanut butter. I use and recommend Member's Mark Natural no-stir Peanut Butter and/or JIF Natural no-stir Peanut Butter. Regular creamy JIF works fine too, but it has a few extra ingredients in there that I prefer not to ingest.
Light brown sugar. A complete must. This ingredient gives the cake a depth of flavor and great texture, and the molasses in brown sugar compliments the peanut butter flavor well.
Buttermilk. This gives the cake a little bit of tang (and makes it addictive). Make your own buttermilk by mixing 1 cup of milk or a plant-based milk alternative like almond milk with 1 tbsp. of white vinegar or lemon juice. Let it sit for 5 minutes, then use it as directed.
Pure vanilla extract.
Vegetable oil. This is what makes the cake crumb so super moist and tender. I highly recommend not using coconut oil in this recipe, as coconut oil becomes solid at room temp. which could make this cake very dry.

How to Make Peanut Butter Cake:

Preheat the oven to 350 F. Prepare a 9x13 sheet pan by greasing it with butter or non-stick cooking spray.
In a medium-sized mixing bowl, sift all-purpose flour, baking powder, baking soda, and salt. Set aside.
In a large-sized mixing bowl or bowl of a stand-mixer, add peanut butter, oil, and brown sugar. Beat until smooth and well-combined. I use a handheld electric mixer. Add in the eggs and vanilla extract; beat until just combined.
Alternately add the flour mixture and buttermilk to the wet ingredients and beat until just combined. The batter should be quite thin (unlike most cakes) and a little bubbly. (See the last photo to the right above.) Note: Consistency may change if you replace it with a different GF flour or regular AP flour.
Pour the batter into the prepared sheet pan.

Bake for 15-20 minutes, until a toothpick inserted in the center comes out clean. I recommend starting with the lowest time to prevent the cake from drying out. It cooks fairly quickly, and all oven times and temperatures vary.
Remove from oven and allow to cool 5 minutes in the pan before inverting and removing. Cool on a wire rack until completely cool, about 1-2 hours.

How to Make Fluffy Peanut Butter Frosting:

First of all, do you know the difference between icing and frosting? Icing is thinner than frosting but not nearly as thin as a glaze. It's typically made with powdered sugar and a liquid such as milk. The frosting is thick, spreadable, and uses fat as a base such as butter, like in this recipe.

In a medium-sized mixing bowl, add butter and peanut butter. Beat until smooth and creamy.
Add in half of the powdered sugar, continuing to beat until just combined. Then, add in the other half.
Add in heavy cream, up to ¼ cup, and beat until you reach a spreadable, fluffy consistency. This frosting is meant to be stiff, don't over-add heavy cream. I tend to add just under ¼ cup.

Spread peanut butter frosting on the cooled cake using a silicone spatula. Be gentle with working it over the cake to prevent any of the cake from tearing.

Add chopped unsalted peanuts to the top of this cake for some texture and visual appeal. I didn't have any on hand, so simple we'll be. Look at that glorious peanut butter frosting.

Serve. You can store leftovers at room temperature, but we actually prefer to eat this cake chilled from the refrigerator.

Finn-approved. I made the version of his cake with a more peanut butter-focused icing with less sugar. (Also, make sure there is no Xylitol in your peanut butter if your dog is partaking, as it is toxic to dogs.)

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