Preheat the oven to 350 °F.
Spray a 9-inch round cake pan lightly with cooking spray.
Place the flour, sugar, cocoa powder, baking soda, and salt in a large bowl. Stir to combine.
Add the vegetable oil, vinegar, vanilla extract, and water. Stir until smooth.
Pour the batter into the prepared pan.
Bake for 25 to 30 minutes or until a toothpick inserted in the center comes out clean or with a few moist crumbs (no wet batter).
Remove the cake from the oven; cool completely in the pan on a wire rack.
Enjoy as is, sprinkle with powdered sugar, frost with your favorite frosting, or top with a dollop of whipped cream.