First, preheat your oven to 350°F and set an oven rack in the lower third of the oven. Prepare the cake pans with baking spray and lined parchment paper.
One hour before baking, in a glass cup measurer, whisk cocoa powder with the boiling water until smooth. Add the oil, and then let cool until room temperature. Make sure to also leave out the butter and eggs to room temperature.
Add flour, sugar, baking powder, and salt into your stand mixer and then whisk on low until blended.
Add the butter and cocoa mixture and manually mash the butter and cocoa before mixing so it doesn't get everywhere. Then, mix on low speed until moistened. Raise the speed to medium and beat for 1½ minutes. Scrape down the bowl.
In a small bowl, crack the eggs, and add water and vanilla extract. Whisk until lightly combined. On medium-low speed, add the egg mixture in three parts, waiting 20 seconds between each part to let the egg incorporate gradually.
Pour the batter into each pan until they are about half full. (Don't overfill!)
Bake for 38-40 minutes, or until a skewer poked in the cake comes out clean.
Once done, let the cakes cool for 10 minutes in their pans on wire racks. Then, let the cakes cool in your fridge for 1 hour.
Once the cakes are cool, run a spatula around the pans and carefully invert the cakes so they come out. The cakes have likely risen to domed tops in the oven, so gently slice the tops off so they are even and ready to decorate.