Step 1

Preheat the oven to 350°F. Choose your pan(s); this recipe will fit two 9" round cake pans, three 8" round cake pans, or a 9" x 13" pan. Grease the pan(s) or line with parchment.

Step 2

, In the bowl of a stand mixer fitted with the flat beater attachment or working in a large bowl with a handheld electric mixer, combine the peanut butter, butter, and brown sugar. Mix until smooth. Scrape down the sides of the bowl and add the vanilla, baking powder, and salt. Beat in 2 of the eggs, then about 1/4 cup (30g) of the flour (this will keep the batter from curdling).

Step 3

, Beat in the 3 remaining eggs one at a time. Scrape the bowl again and add 1/3 of the remaining flour to the batter, beating gently to combine. Gently beat in half the milk. Mix in half of the remaining flour, then the remaining milk. Stir in the remaining flour. Scrape the bowl once more, and beat for another 30 seconds.

Step 4

, Divide the batter between the prepared pan(s) and level the top. (The total weight of the batter is about 1530g, if you’re weighing the batter evenly into your pans.)

Step 5

, Bake the peanut butter cake(s) for 33 to 35 minutes for 9" layers, 30 to 33 minutes for 8" layers, or 45 minutes for a 9" x 13" cake, until the top springs back when lightly pressed in the center and the edges just begin to pull away from the sides of the pan.

Step 6

, Remove the peanut butter cake(s) from the oven and cool in the pans on a rack for 20 minutes. Then turn the cakes out of the pans and return them to the rack to cool completely before frosting.

Step 7

, Storage information: After cooling, peanut butter cake layers can be wrapped and frozen for up to 2 months; once frosted, the peanut butter cake can be kept at room temperature for several days; freeze for longer storage.