1. In a large mixing bowl, whisk together the flour, sugar, cocoa powder, baking powder, baking soda, and salt.
2. Add the milk, vegetable oil, eggs, and vanilla extract. Beat on medium speed until smooth and well combined.
3. If using, stir in the boiling water last—the batter will be thin, but this ensures a lighter texture.

Step 3: Bake the Cake Layers

Divide the batter evenly between the prepared pans. Smooth the tops with a spatula. Bake for 25–30 minutes, or until a toothpick inserted into the center comes out clean. Let the cakes cool completely before assembling.