Preheat oven to 350F. Start by combining the cocoa powder with the boiling water in a small bowl until smooth and let it cool to room temperature.
In a medium bowl lightly combine eggs, 1/4 of the cocoa mixture, and vanilla. I use vanilla bean powder, but that's only my preference. The liquid version works just fine.
In a large mixing bowl combine all remaining dry ingredients on low speed for about 30 seconds.
Next, add the butter and remaining cocoa mixture, also on low speed until the dry ingredients are moistened. Then, and only then, increase mixing speed to medium. Otherwise you, your counter, mixer, and kitchen will be covered in a flour cloud for while. Beat for a couple minutes to fully combine the ingredients, scrape down bowl when necessary. Add the egg mixture in 3 parts, mix for about 20 seconds after each addition and scrape down the sides. Do not over-mix at this step. It will mess with your cake structure.
Fill your greased, lined, and floured cake pans with the batter (I also sprinkled a few chocolate chips on top for this one) and bake for 25-35 minutes. Somehow I forgot to take a picture of this step until the pans were in the oven already.
The cake layers are done when the top springs back after pressing down lightly and an inserted skewer or toothpick comes out clean.