Preheat oven to 350 degrees F (175 degrees C). Grease 3 - 9 inch round cake pans. In medium bowl, pour boiling water over cocoa, and whisk until smooth. Let mixture cool. Sift together flour, baking soda, baking powder and salt; set aside.
In a large bowl, cream butter and sugar together until light. Beat in eggs one at time, then stir in vanilla. Add the flour mixture alternately with the cocoa mixture. Spread batter evenly between the 3 prepared pans.