Prep your pans and oven: Preheat to 350°F (175°C). Grease and line two 8-inch round cake pans with parchment circles.
Lightly flour the sides.
Whisk dry ingredients: In a medium bowl, whisk 2 1/2 cups all-purpose flour, 1 1/2 cups granulated sugar, 2 tablespoons unsweetened cocoa powder, 1 teaspoon baking soda, and 1 teaspoon salt.
Combine wet ingredients: In a large bowl, whisk 1 cup buttermilk, 3/4 cup neutral oil, 2 large eggs, 2 teaspoons vanilla extract, 1 teaspoon white vinegar, and 1 to 1 1/2 tablespoons red gel food coloring. Adjust color as needed—batter should be bright red because it will darken slightly as it bakes.
Bring it together: Add the dry ingredients to the wet in two additions, whisking gently until just combined. Do not overmix.
The batter should be smooth and pourable.
Fill the pans: Divide batter evenly between the prepared pans. Tap each pan lightly on the counter to release any big air bubbles.
Bake: Bake 25–30 minutes, or until a toothpick comes out with a few moist crumbs. The tops should spring back when lightly pressed.
Cool completely: Let cakes cool in the pans for 10 minutes, then turn out onto a wire rack, remove parchment, and cool fully.
Chilling layers for 30–45 minutes before frosting makes assembly easier.
Make the frosting: Beat 12 ounces cream cheese and 3/4 cup unsalted butter on medium speed until smooth and fluffy, about 2–3 minutes. Add 3 1/2 to 4 cups powdered sugar, 1 teaspoon vanilla, and a pinch of salt. Beat on low to combine, then on medium until creamy and spreadable.
If too soft, chill for 10–15 minutes.
Assemble: Place one cake layer on a serving plate. Spread a generous layer of frosting over the top. Set the second layer on top and press gently.
Crumb coat: Spread a thin layer of frosting over the entire cake to seal in crumbs.
Chill for 20–30 minutes.
Finish frosting: Add a final, thicker coat and smooth with an offset spatula. For a simple finish, swirl the top and add sprinkles or a few fresh berries.
Slice and serve: For clean slices, warm a knife in hot water, wipe dry, and cut. Enjoy slightly chilled or at room temperature.