Preheat your oven to 350°F (175°C).

Grease a 13x18 inch jelly roll pan or a 9x13 inch baking pan.

In a large bowl, whisk together 2 cups of all-purpose flour, 2 cups of granulated sugar, 1 teaspoon of baking soda, and ½ teaspoon of salt.

In a saucepan over medium heat, combine ¾ cup unsalted butter, ½ cup creamy peanut butter, and 1 cup of water. Heat until melted and smooth.

Remove from heat and stir in 1 cup of milk and ½ teaspoon of vanilla extract, then whisk in 2 large eggs, one at a time.

Pour the wet ingredients into the dry ingredients and stir until smooth.

Pour the batter into the prepared pan and spread evenly.

Bake for 20-22 minutes, or until a toothpick inserted into the center comes out clean.

Let the cake cool in the pan for 15-20 minutes.

Spread the peanut butter frosting over the cooled cake.