Preheat oven to 350º F (176ºC) and thoroughly spray two 9-inch round cake pans with a non-stick cooking spray.
In a medium bowl, combine flour, sugar, cocoa powder, salt, baking soda, and baking powder.
In a large bowl, use an electric mixer to beat oil, buttermilk, eggs, and vanilla. Add the dry ingredients from the medium bowl, combine and mix on low speed. Don’t overmix. Add water and mix again to combine it all together. Don’t overmix. Don’t worry, the batter will be thin.
Pour the batter into the pans and bake for 25 min or just until a toothpick/fork poked into the center comes out clean. Cool for 10 minutes before removing cakes from the pans.
In a medium bowl, stir together melted butter and cocoa. Add milk, vanilla, and powdered sugar. Using an electric mixer, beat well to combine.
Frost the first cake layer with approximately half (or just a tad less) of the frosting. Add the top cake layer and finish frosting the cake all over. Enjoy this one! It’ll be the best chocolate cake you’ve ever tasted. 100%.