Preheat oven to 350°F. Grease and flour three 9-inch round cake pans.
In a large bowl, mix sugar, flour, cocoa, baking powder, baking soda, and salt.
Add eggs, milk, oil, and vanilla. Beat on medium speed for 2 minutes.
Stir in boiling water (batter will be thin). Pour evenly into prepared pans.
Bake 30–35 minutes or until a toothpick comes out clean.
Cool in pans for 10 minutes, then remove to wire racks to cool completely.