Prepare cake batter: In a large size bowl, or in the bowl of your mixer, combine the flour, sugar, cocoa, leavening agents, and salt. In a separate bowl, mix together the wet ingredients; buttermilk, oil, eggs, and vanilla. Next, add the wet ingredients to the dry ingredients in the large bowl, and mix. Keep the mixer on low speed and slowly add in the prepared coffee - continue mixing until everything is well combined and smooth. Finally, scrape the bottom of the bowl with a spatula and mix again as needed.