Ingredients:

  • 2.5 cups all-purpose flour (315g)
  • 1.5 cups granulated sugar (300g)
  • 0.5 cup light brown sugar, packed (100g)
  • 1 tsp baking soda
  • 1 tsp baking powder
  • 0.75 tsp kosher salt
  • 0.75 cup creamy peanut butter (190g)
  • 0.5 cup unsalted butter, softened (115g)
  • 3 large eggs, room temperature
  • 1 cup buttermilk, room temperature (240ml)
  • 2 tsp vanilla extract
  • 1 cup unsalted butter for frosting, softened (225g)
  • 1 cup creamy peanut butter for frosting (250g)
  • 3.5 cups powdered sugar, sifted (440g)
  • 4 tbsp heavy cream
  • 1 tsp vanilla extract for frosting
  • 1 pinch salt

Instructions:

  1. Preheat your oven to 350°F (175°C) and grease a 9x13 inch baking pan.
  2. In a large mixing bowl, whisk together the all-purpose flour, baking soda, baking powder, and kosher salt. Set aside.
  3. In a stand mixer, beat the softened butter, 3/4 cup creamy peanut butter, granulated sugar, and light brown sugar for at least 3 minutes until pale and aerated.
  4. Add the eggs one at a time, ensuring each is fully incorporated before adding the next. Stir in the vanilla extract.
  5. Alternately add the dry ingredients and the buttermilk to the creamed mixture, beginning and ending with the dry ingredients. Mix until just combined.
  6. Pour the batter into the prepared 9x13 pan and bake for 35 minutes, or until a toothpick inserted into the center comes out clean.
  7. Prepare the frosting by beating 1 cup butter and 1 cup peanut butter until smooth. Gradually add powdered sugar, heavy cream, and vanilla. Whip on high speed until light and fluffy.
  8. Allow the cake to cool completely in the pan before spreading the peanut butter frosting over the top.