Pre-heat oven to 350º F. Grease three 8-inch or two 9-inch round cake pans with cooking spray and lightly dust with flour. I like to do 3 8×8 pans.
In mixing bowl (Stand Mixer), add flour, sugar, cocoa, baking powder, baking soda, and salt. Stir until well combined.
Add milk, oil, eggs, and vanilla to flour mixture and mix together on medium speed until well mixed. Reduce the speed to low and add boiling water to the cake batter a little bit at a time. Once the water is all mixed in, beat on high for about 1 minute.
Evenly distribute cake batter between the three 8×8 pans (or two 9×9) prepared cake pans.
Bake for 30-35 minutes, or until a toothpick or cake tester inserted in the center comes out clean.
Remove from the oven and allow to cool for about 10 minutes. Remove from the pan and cool completely.
Chocolate Buttercream Frosting: