The Vintage Peanut Butter Cake I Bake on Repeat

Preheat the oven to 325°F. Grease two 8-inch nonstick cake pans with cooking spray on the bottom but not the sides–this helps the cakes grip the edges and rise properly. Set aside.

Make the cake batter: In a medium saucepan, melt the butter over medium heat. Remove the pan from the heat and whisk in the brown sugar, peanut butter, eggs, sour cream, water, vanilla, and salt until very smooth. Sprinkle on the flour and baking powder and whisk vigorously until a smooth batter forms, at least 30 seconds. Don't be afraid of overmixing–you need to whisk vigorously to break up any clumps, and there's enough fat in this batter to preserve a tender texture.

Bake the cakes: Divide the batter evenly between the prepared cake pans and bake until the center of the cakes springs back when lightly touched, 35 to 40 minutes. Allow to cool in the pans on a cooling rack for at least 45 minutes.

Make the frosting: In a medium bowl, combine the butter, powdered sugar, peanut butter, milk or water, vanilla, and salt. Use a hand mixer to slowly incorporate all of the ingredients, starting on low speed to avoid a powdered sugar cloud. Once the ingredients come together, increase the mixer speed to high and beat for about 1 minute until fluffy and lightened in color.

Assemble the cake: Once the cakes are completely cool to the touch, run a butter knife around the edge of the pans to release the sides of the cakes. The cakes should pop right out when inverted, but if they're being a little stubborn, use the butter knife, pressing against the side of the cake to gently coax it out of the tin. Flip one of the cake layers upside-down and place it on a serving plate—this will create a flat surface for easier frosting and stacking. Top with about 1/3 of the frosting, spreading it on top of the cake with the back of a spoon. Place the second cake layer on top, right-side up, and generously dollop on the remaining frosting, spreading it to cover the top and sides. Use the back of the spoon to make swoops and swirls all over the cake. Cover and store at room temperature for up to 3 days. You can invert a large bowl over the serving plate, use a cake keeper, or cut into slices and wrap individually.