Preheat oven to 350°F (175°C). Grease two 8-inch round cake pans and line the bottoms with parchment paper; grease the parchment. Lightly dust pans with flour or cocoa and tap out excess.

Whisk dry ingredients: In a large bowl, sift or whisk together the all-purpose flour (2.5 cups), granulated sugar (1.5 cups), unsweetened cocoa powder (2 tbsp), baking soda (1 tsp), baking powder (1/2 tsp) and fine sea salt (1/2 tsp) until evenly combined.

Combine wet ingredients: In a separate medium bowl, whisk together the vegetable oil (1 cup), buttermilk (1 cup), eggs (2), vanilla extract (1 tsp), and white vinegar (1 tsp). Mix until smooth and homogeneous.

Add food coloring: Stir the red food coloring (2 tbsp) into the wet mixture until color is uniform. If using gel coloring, scrape and mix thoroughly; adjust by up to 1 tbsp more if you prefer a deeper red.

Create batter: Make a well in the center of the dry ingredients. Pour the wet mixture into the well and gently fold with a spatula or low-speed mixer until just combined. Do not overmix. Batter will be fairly thin.

Activate lift: Mix the distilled white vinegar (1 tsp) into 2 tablespoons of warm buttermilk (taken from the total) or simply stir into the batter; this, together with baking soda, helps produce a tender crumb. Fold in quickly and pour batter evenly between the prepared pans.

Bake: Place pans on the middle rack and bake for 25–30 minutes, rotating halfway through, until a toothpick inserted near the center comes out with a few moist crumbs but no wet batter and the cakes spring back lightly when touched.

Cool: Let cakes rest in pans for 10 minutes, then run a thin knife around edges and invert onto a wire rack. Peel off parchment and allow to cool completely (about 1 hour) before frosting. Reserve any trimmings for garnish.

Cream Cheese Frosting

Chill equipment briefly: If your kitchen is warm, chill mixing bowl and beaters for 5–10 minutes. This helps keep the frosting stable.

Beat butter and cream cheese: In a large bowl, beat the softened unsalted butter (1/2 cup) and softened cream cheese (8 oz) together on medium speed until smooth and fully combined, about 2–3 minutes. Scrape down the sides as needed.

Add sugar gradually: With the mixer on low, gradually add the sifted confectioners' sugar (3 cups) in two or three additions to avoid a sugar cloud. Once incorporated, increase speed to medium and beat until smooth and fluffy, about 2–3 minutes. If frosting seems too thick, beat in the optional sour cream (up to 2 tbsp) one tablespoon at a time to reach spreading consistency.

Finish frosting: Mix in the vanilla extract (1 tsp) and fine sea salt (1/4 tsp). Taste and adjust salt or vanilla as needed. Chill briefly (10–15 minutes) if the frosting is too soft to spread.

Assembly & Finish

Level and trim: If cake layers are domed, level them with a serrated knife to create even layers. Reserve trimmings for crumbs.

First layer: Place one cake layer (flat side up) on a serving plate or cake board. Spread about one-third of the cream cheese frosting over the top in an even layer (about 1/3 of total frosting).

Second layer: Gently place the second cake layer on top (flat side down). Press lightly to adhere. Apply a thin crumb coat of frosting over the entire cake using about 1/3 of the frosting to trap crumbs. Chill the cake for 15–20 minutes to set the crumb coat.

Final frosting: Apply the remaining frosting in an even layer over the top and sides. Smooth with an offset spatula or create decorative swirls as desired.

Garnish: Press reserved crumbs (about 1/2 cup) around the base or sprinkle on top for a classic red velvet look. Refrigerate the cake for at least 30 minutes to set before slicing.

Storage and serving: Store covered in the refrigerator for up to 4 days. Remove from fridge 20–30 minutes before serving to soften the frosting for easier slicing.