Heat oven to 350 degrees. Grease and flour an 8-inch square baking pan; set aside.
In a large mixing bowl, whisk together flour, sugar, cocoa, baking soda, and salt. Add water, oil, vinegar, and vanilla extract and stir until smooth and thoroughly combined. Pour batter into prepared pan. Bake 30-35 minutes or until a toothpick inserted in the center comes out clean. Cool completely on a wire rack. Frost as desired.
Note: There are no eggs in this recipe, so their omission from the list of ingredients is not an error.