Preheat the Oven

• Preheat your oven to 350°F (175°C).
• Grease a 10×15-inch jelly roll pan (for a thinner cake) or a 9×13-inch baking pan (for a thicker cake).

Prepare the Dry Ingredients

• In a large bowl, whisk together flour, granulated sugar, brown sugar, baking soda, and salt.

Heat the Wet Ingredients

• In a saucepan over medium heat, combine water, butter, and peanut butter.
• Stir continuously until smooth and bring to a gentle boil.
• Remove from heat.

Mix the Batter

• Pour the hot peanut butter mixture into the dry ingredients. Stir until well combined.
• Add vegetable oil, buttermilk, eggs, and vanilla extract. Mix until smooth.

Bake the Cake

• Pour the batter into the prepared pan, spreading it evenly.
• Bake for 20-25 minutes, or until a toothpick inserted in the center comes out clean.

Prepare the Frosting

• While the cake bakes, heat butter, peanut butter, and buttermilk in a saucepan over medium heat.
• Stir until smooth and bring to a gentle boil.
• Remove from heat and gradually whisk in powdered sugar and vanilla extract until smooth.

Frost the Cake

• Let the cake cool for 15 minutes after baking.
• Pour the warm frosting over the warm cake, spreading evenly.

Cool & Serve

• Allow the cake to cool completely before slicing and serving.