In large mixing bowl, whisk together flour, sugar, cocoa powder, baking powder, baking soda, and salt. Add buttermilk, brown sugar, eggs, oil and vanilla. Beat with electric mixer on medium speed 2 minutes. Whisk in hot coffee. (Batter will be quite thin.) Pour batter into greased, floured 12-cup bundt pan. Bake in preheated 350F oven 60 minutes or until tester inserted comes out clean. Cool on rack 10 minutes. Remove from pan; cool. ----