Preheat oven to 350°F. Line two 10.75 in x 7.8 in. oval baking pans with parchment paper; spray with vegetable pan spray.
In large bowl, combine flour, sugar, cocoa, baking soda and salt; whisk until well blended (if necessary, sift cocoa before adding). In medium bowl, combine water, oil, vanilla and vinegar. Add liquid ingredients to dry ingredients and whisk until just blended.
Divide batter into prepared pans. Bake 36-38 minutes or until toothpick inserted in center comes out clean. Cool 10 minutes in pan. Unmold onto cooling grid; cool completely.
Makes two 10-in. oval cake layers; about 12 servings.
Variation: Bake this cake in two 8 in. round or square baking pans.