1. Heat oven to 350 degrees F. Grease pans; line bottoms with waxed paper; grease paper; dust pans with flour.
2. On low speed, mix flour, sugar, cocoa, baking soda, baking powder and salt in large bowl until mixed.
3. Add eggs, buttermilk, water, butter and vanilla; beat 30 seconds on low, until dry ingredients are moistened. Increase to medium; beat 2 minutes. Pour into prepared pans.
4. Bake in 350 degrees F oven for 45 minutes for 9-inch rounds and hearts, or 40 to 45 minutes for 9-inch squares, or until wooden pick inserted in center comes out clean.
5. Cool pans on rack 10 minutes. Remove cakes to rack to cool.