Preheat your oven to 325°F. Prepare three 8-inch cake pans by lining them with parchment rounds and generously spraying the parchment and sides with nonstick cooking spray.
In a glass measuring cup, mix the hot coffee and cocoa powder, then cover and let it sit for 5 minutes.
In a medium-sized mixing bowl, whisk together the flour, baking powder, baking soda, salt, and cinnamon.
In a large mixing bowl, combine the sugar, vegetable oil, and melted butter, whisking until very well mixed. Add the eggs and egg yolk, whisking vigorously for about twenty seconds. Pour in the buttermilk, vanilla extract, and food coloring, and mix well. Stir in the vinegar and coffee-cocoa mixture.
Gradually sift the flour mixture into the batter using a fine mesh sieve, adding it in three parts and whisking well after each addition.
Evenly divide the batter among the prepared cake pans. Tap the bottoms of the pans on the counter several times to release any trapped air bubbles.
Bake for 25 to 30 minutes, or until a cake tester or toothpick inserted into the center comes out clean. It's normal for the cakes to appear slightly spongy on top. Allow the cakes to cool in the pans on wire racks. Once cool enough to handle, run a thin knife around the edges to loosen the cakes, then invert them onto the racks to cool completely.