Preheat oven to 350 degrees Fahrenheit.

Grease and flour a 13x9 inch baking pan or two 9 inch round cake pans.

In a medium bowl, whisk together flour, cocoa, baking powder, baking soda, and salt.

In a large mixer bowl, beat butter, sugar, and vanilla extract until creamy.

Add eggs one at a time, beating well after each addition.

Gradually add the flour mixture to the wet ingredients, alternating with water, until the batter is well combined and smooth.

Pour the batter into the prepared cake pan.

Bake for 25-35 minutes, or until a toothpick inserted into the center comes out clean.

Let the cake cool in the pan for 15 minutes.

Turn the cake onto a wire rack to cool completely.

Decorate with your favorite frosting.