Prep the pans and oven. Heat oven to 350°F (175°C).
Grease and line two 8-inch round cake pans with parchment. Lightly flour the sides or use baking spray with flour.
Whisk dry ingredients. In a medium bowl, whisk 2 1/2 cups all-purpose flour, 2 tablespoons natural cocoa powder, 1 teaspoon baking soda, and 1/2 teaspoon fine sea salt. Set aside.
Cream butter, oil, and sugar. In a large bowl, beat 1/2 cup softened unsalted butter with 1/2 cup neutral oil and 1 3/4 cups granulated sugar until light and fluffy, about 2–3 minutes.
Add eggs and vanilla. Beat in 2 large eggs, one at a time, then add 2 teaspoons vanilla extract.
Scrape the bowl so everything mixes evenly.
Color and acid. Stir 1 cup buttermilk with 1 teaspoon distilled vinegar and add red gel food coloring. Start with 1–2 teaspoons gel and adjust until the color looks deep but not neon.
Combine wet and dry. Add the dry ingredients to the butter mixture in three parts, alternating with the red buttermilk mixture. Begin and end with dry ingredients.
Mix on low just until smooth; don’t overmix.
Pan and smooth. Divide batter evenly between pans. Tap each pan once on the counter to release air bubbles. Smooth the tops with a spatula.
Bake. Bake 25–30 minutes, or until a toothpick comes out with a few moist crumbs.
The tops should spring back lightly when touched.
Cool completely. Let cakes cool in pans 10 minutes, then turn onto a rack. Peel off parchment. Cool fully before frosting.
Make cream cheese frosting. Beat 12 ounces cream cheese (room temp) with 1/2 cup unsalted butter (room temp) until smooth.
Add 3–3 1/2 cups powdered sugar, 1 teaspoon vanilla, and a pinch of salt. Beat until fluffy. Add 1–2 tablespoons heavy cream or milk to reach a silky, spreadable consistency.
For extra tang, add 1 teaspoon lemon juice.
Assemble. Level cake tops if needed. Place the first layer on a stand, spread frosting generously, then add the second layer. Apply a thin crumb coat, chill 20 minutes, then finish with a smooth final layer.
Add simple swirls on top if you like.
Set and serve. Chill 20–30 minutes to set the frosting. Slice with a warm knife for clean edges.