
Preheat oven to 325°F and line three 8-inch round cake pans with parchment rounds.
Spray parchment and sides of pans generously with nonstick cooking spray.
In a glass measuring cup, whisk the hot coffee and cocoa powder together, then cover and let stand for 5 minutes.
In a medium mixing bowl, whisk together the flour, baking powder, baking soda, salt, and cinnamon.
In a large mixing bowl, whisk together the sugar, vegetable oil, and melted butter. Add in the eggs and egg yolk and whisk for around twenty seconds (or until very well combined). Add in the buttermilk, vanilla, and red food coloring and whisk to combine. Whisk in the vinegar and coffee mixture.
Using a fine mesh sieve, sift the flour mixture into the batter in three additions, whisking until each addition is incorporated.
Divide the batter equally between the prepared pans, then tap the bottoms of the pans against the counter several times to release any air bubbles.
Bake for 25 to 30 minutes, or until a cake tester or toothpick inserted into the center comes out clean.
Place the cake pans on cooling racks, and when they’re cool enough to touch, run a thin knife around the edges of the pans to loosen the cakes. Invert onto the wire racks and let cool completely.
In the bowl of a stand mixer fitted with the paddle attachment, beat the softened butter and sifted powdered sugar on low. Gradually increase to medium-high to prevent a sugar cloud.
Beat for 3 minutes until the mixture is pale, light, thick, but smooth. It may look dry or crumbly at first, but keep beating until it holds together.
Scrape down the bottom and sides of the bowl and paddle, then add the cream cheese and beat on medium-high for 1 minute until fluffy.
Add the vanilla and salt and beat for 30 seconds until fully incorporated. Scrape down the bowl again as needed.
Lay one cake layer flat-side up on a cake plate or pedestal. Tuck in strips of baking paper under the cake edges to keep the plate clean.
Use about a third of the frosting to fill the bottom cake layer, then top with the second cake layer and repeat.
Place the final cake layer flat-side up and use the remaining frosting to ice the whole cake.