Preheat oven to 350°F (175°C). Line two 9-inch cake pans with parchment paper circles and grease the pans well.
In a medium bowl, whisk together flour, cocoa powder, baking soda, and salt until evenly combined. Set aside.
In a large bowl, beat sugar and vegetable oil with an electric mixer until well combined. Add eggs one at a time, beating well after each addition. Mix in vanilla.
With mixer on low, gradually add buttermilk and vinegar, then mix in red food coloring until the batter is uniformly red.
Gradually add the dry ingredients to the wet mixture on low speed, mixing just until combined. Scrape down the bowl and fold gently with a spatula.
Divide batter evenly between the prepared pans and smooth the tops. Bake for 28–32 minutes until a toothpick comes out with a few moist crumbs.
Let cakes cool in the pans for 15 minutes. Run a knife around the edges, invert onto a wire rack, peel off the parchment, and cool completely for 1–2 hours.
Beat room-temperature cream cheese until smooth and fluffy. Add butter and beat until creamy. Gradually beat in sifted powdered sugar on low speed, then add vanilla and salt.
Increase speed to medium-high and beat for 2–3 minutes until the frosting is light and spreadable. Refrigerate if too soft.
Level the cooled cake layers with a serrated knife. Place one layer on a plate or turntable and spread 1–1½ cups of frosting evenly over the top.
Top with the second layer and apply a thin crumb coat of frosting over the entire cake. Chill for 20–30 minutes until firm.
Apply the remaining frosting to the top and sides, creating a smooth or rustic finish. Decorate with cake crumbles if desired.