Heat oven to 350°F. Grease and flour two 9-inch round cake pans. Set aside.
Stir together sugar, flour, cocoa, baking powder, baking soda and salt in a large bowl. Add eggs, milk, oil and vanilla; With a mixer, beat on medium speed for about 2 minutes. Carefully, stir in boiling water. The batter will be very thin. Pour batter into prepared cake pans.
Bake for 30 to 35 minutes or until a toothpick inserted in center comes out clean. Cool 10 minutes; remove from pans to wire racks. Cool completely. Frost with chocolate frosting.
*Before high altitude changes: 2 cups sugar, 1-½ teaspoons baking powder, 1-½ teaspoons baking soda, 1 cup milk
Perfectly Chocolate Chocolate FrostingMelt butter. Stir in cocoa. Alternately add powdered sugar and milk, beating to spreading consistency. Add small amount additional milk, if needed. Stir in vanilla. About 2 cups frosting.