Prepare the cake batter: Preheat your oven to 350°F (175°C). Grease and line two 9-inch round cake pans with parchment paper. In a bowl, sift together flour, baking soda, salt, and cocoa powder. In a separate small bowl, whisk buttermilk, vinegar, vanilla, and red food coloring until the mixture has an even, vibrant color.

Cream the butter and sugar: In a large mixing bowl, beat the butter and sugar together with a mixer on medium speed until light and fluffy, about 3–4 minutes. Add eggs one at a time, mixing well after each addition. Reduce mixer speed to low, and gradually alternate between adding the dry ingredients and the colored buttermilk mixture. Continue mixing until just combined and smooth, but avoid overmixing to keep the cake tender.

Bake the cakes: Divide the batter evenly between the prepared pans, smoothing the tops with a spatula. Bake for 30–35 minutes or until a toothpick inserted into the center comes out clean. Let the cakes cool in their pans for 10 minutes before transferring them to a wire rack to cool completely.

Make the cream cheese frosting: In a large bowl, beat the cream cheese and butter together until smooth and creamy. Gradually add powdered sugar, one cup at a time, while mixing on low speed. Once incorporated, increase speed to medium-high and beat until fluffy. Add vanilla extract and a pinch of salt, then mix again until well blended.

Assemble the cake: Once the cake layers are completely cool, spread a thick layer of frosting on top of one cake. Place the second layer over it, and frost the top and sides evenly. For a smooth finish, use an offset spatula dipped in warm water. If desired, crumble some cake trimmings or red velvet crumbs over the top for decoration.

Chill and serve: Refrigerate the cake for about 30 minutes before serving to help it set. Slice into generous pieces and serve slightly chilled or at room temperature for the best flavor and texture.