Preheat oven to 350°F. Line and grease your cake pans with parchment and cocoa powder to ensure the sponges release perfectly without a floury white crust.
Whisk together the flour, sugar, cocoa powder, baking powder, baking soda, and salt. Sifting the dry elements prevents dense, bitter lumps in your finished crumb.
In a separate bowl, combine the buttermilk, oil, room temperature eggs, and vanilla. Room temperature ingredients prevent the oil from seizing, creating a perfectly emulsified batter.
Combine the wet and dry ingredients on low speed, then carefully stream in the boiling water. The heat blooms the cocoa powder, unlocking its deepest flavor profile.
Bake for 30-35 minutes until a toothpick comes out clean. Cool fully on a wire rack.
