Preheat the Oven: Start by setting your oven to 325°F (163°C). Prepare three 8-inch cake pans by lining them with parchment paper and spraying the sides with nonstick cooking spray.
Make the Cocoa Mixture: In a mixing bowl, whisk together the hot coffee and cocoa powder. Let this mixture sit to cool slightly.
Mix the Dry Ingredients: In another bowl, combine the flour, baking powder, baking soda, salt, and optional cinnamon. Set aside.
Blend the Wet Ingredients: In a large bowl, mix together the sugar, vegetable oil, melted butter, eggs, egg yolk, buttermilk, vanilla extract, and red gel food coloring. Blend well until everything is fully combined. Add the cooled cocoa mixture and vinegar, mixing until smooth.
Combine Mixtures: Gradually sift the dry ingredients into the wet mixture, whisking gently to incorporate.
Bake: Pour the batter evenly into the prepared pans. Bake for 25-30 minutes, or until a toothpick inserted in the center comes out clean.
Cool the Cakes: Once baked, let the cakes cool in their pans for about 10 minutes. Carefully run a thin knife around the edges, then invert the cakes onto wire racks to cool completely.