This is a very easy to prepare, moist, 1-layer chocolate cake.
Sift the flour, sugar, cocoa, baking soda, and salt together into a 9" cake pan. Poke 3 holes in the mixture. Mix the vegetable oil, vinegar, and vanilla together. Pour the mixture into the 3 holes. Pour the water over all the ingredients in the pan. Mix with a wooden spoon until the dry ingredients are completely moistened and all the ingredients are well blended. Bake in a preheated oven at 350º for about 30 to 35 minutes or until a toothpick inserted into the center of the cake comes out clean. Remove the cake from the oven and place it on a wire rack to cool completely. Leave the cake in the pan. Spread vanilla or chocolate frosting on top, if desired.