Mix the flour, both sugars, cocoa powder, baking soda and powder, and the salt together in a large mixing bowl until well-blended.
In a separate bowl, combine the oil, eggs, vanilla extract, and the buttermilk. Use a hand mixer to blend everything together, on low speed, for 2 minutes.
Add the dry mixture to the wet mixture and blend on low speed until the flour is moistened. Scrape down the sides of the bowl with a rubber spatula. Blend for 30 seconds on low speed.
Add the coffee, then blend on low speed for 1 minute.
Divide the batter equally between the two pans. Use your rubber spatula to rapidly tap the sides of the cake pans to release any air bubbles within in the batter.
Bake the cakes for 30 minutes, or until a toothpick inserted into the center of the cakes comes out clean, and the sides of the cake pull away from the pans.
Allow the cakes to cool in the pans for 5 minutes before turning them out onto a cooling rack and letting them cool completely.
Wrap the cakes in plastic wrap once they've cooled, and let them rest overnight to develop their structure.