Preheat oven to 350°F and lightly grease baking pans. You can use three 6" pans or two 8" or 9" pans. Line the bottom of the pans with parchment paper for easy removal.
In a large bowl, whisk together the flour, salt, baking powder, baking soda, and sugar. Sift in the cocoa powder, and whisk to combine.
In a medium bowl, whisk together the oil, eggs, vanilla, buttermilk, and coffee. Be sure to temper your eggs or add in the coffee very slowly in order to keep the eggs from cooking.
Pour the wet ingredients into the dry ingredients and beat on medium speed until combined.
Pour the batter into the pans and bake 25-30 minutes or until a toothpick inserted in the center comes out clean.
Let the cakes cool in the pan 5-10 minutes, then remove them and place on a wire rack to cool completely.