Preheat oven to 350°F (175°C). Grease two 9-inch round cake pans and line with parchment paper.
In a medium bowl, sift flour, cocoa powder, baking soda, and salt to create a lump-free batter. Set aside.
In a large bowl, use a stand mixer to cream butter and sugar until light and fluffy, about 2–3 minutes.
Add vegetable oil and mix well. Add eggs one at a time, mixing thoroughly after each.
Pour in buttermilk, red gel food coloring, vanilla extract, and white vinegar. Mix until evenly colored.
Gradually add dry ingredients to wet mixture, mixing on low speed until just combined.
Divide batter evenly between prepared pans. Smooth tops with a spatula.
Bake for 25–30 minutes, until a toothpick poked in the center comes out clean.
Let cakes rest in pans for 10 minutes, then transfer to a cooling rack to cool completely.
For frosting, beat cream cheese and butter until smooth, about 2 minutes.
Gradually blend in powdered sugar, one cup at a time, on low speed. Add vanilla extract and beat until creamy.
Trim cake tops if uneven. Place one layer on a cake stand, spread frosting on top, then add the second layer.
Spread frosting over the top and sides. Smooth with a spatula or create swirls for decoration.