Bring butter, eggs, and cream cheese to room temperature - this is crucial for proper mixing. Sift flour and cocoa together to avoid lumps. Preheat oven to 350°F and grease two 9-inch round pans. Mix food coloring with a bit of water to make it easier to distribute evenly. Have everything measured and ready because this batter comes together fast.

Cream butter and sugar for exactly 4 minutes until light and fluffy. Add eggs one at a time, beating well after each addition. Mix in vanilla and food coloring until evenly distributed. Don't rush this step or your cake will be dense. Scrape bowl sides constantly for even mixing.

Alternate adding flour mixture and buttermilk in 3 additions, starting and ending with flour mixture. Mix on lowest speed just until flour disappears. Stir vinegar and baking soda together until it foams like crazy. Fold this foaming mixture gently into batter by hand with rubber spatula.

Divide batter evenly between prepared pans using kitchen scale if you have one. Bake exactly 28 minutes for 9-inch pans until toothpick comes out with few moist crumbs. Cool in pans 10 minutes, then turn out onto wire racks. Cool completely before frosting - about 1 hour.

Beat cream cheese and butter until completely smooth with no lumps. Gradually add powdered sugar while beating until frosting holds peaks and looks glossy. Add vanilla and salt, beat until combined. Frosting should be smooth and spreadable.

Place first layer on serving plate and spread frosting evenly on top. Add second layer and frost top and sides using offset spatula for smooth finish. Refrigerate 30 minutes to set frosting before serving.