Preheat oven to 350°
In a medium bowl, combine cocoa with boiling water, mix until smooth and cool to room temperature.
Grease and flour sides of 3 9" cake pans, line bottoms with parchment paper.
Sift together flour, soda, baking powder, and salt. Set aside.
Beat butter, sugar, eggs, and vanilla at high speed until light, about 5 minutes.
Reduce mixer to low speed and alternate flour mixture (in 4ths) with cocoa mixture (in 3rds) beginning and ending with the flour. DO NOT OVERBEAT.
Scrape sides and bottom of mixing bowl, beat additional 15 seconds to make sure batter is completely mixed.
Divide batter evenly between cake pans. Bake at 350° for 25-30 minutes or until pick comes out with just a few moist crumbs attached.
Cool in pans for 10 minutes then invert onto wire rack and cool completely. Remove parchment paper before frosting.