PREHEAT oven to 350° F. Grease and flour two 9-inch-round baking pans or one 13 x 9-inch baking pan.
COMBINE flour, cocoa, baking powder, baking soda and salt in medium bowl. Beat butter, sugar and vanilla extract in large mixer bowl until creamy. Add eggs one at a time, beating well after each addition. Gradually beat in flour mixture alternately with water. Spread into prepared pan(s).
BAKE for 25 to 35 minutes or until wooden pick inserted in center comes out clean. Cool in pan(s) for 15 minutes; invert onto wire racks to cool completely.
FROST with Chocolate Lover's Frosting