Grease and flour 3 9" round cake pans. I like to also line the pans with parchment paper and lightly grease the paper.
In a large bowl, sift together the flour, soda, salt, and cocoa. Set aside.
In a separate large mixing bowl or stand mixer, cream the butter and oil for about 3 minutes then add the sugar. Cream together until light and fluffy.
Add eggs and vinegar.
Mix until just combined.
Add flour mixture alternately with buttermilk to egg mixture, mixing after each addition.
Add vanilla and food coloring, mixing well.
Pour batter evenly into prepared cake pans and bake for 20-25 minutes or until done.
Frost with cream cheese icing or cooked white icing.
In a large mixing bowl, beat the cream cheese and butter until fluffy.
Add sugar a little at a time, scraping down the sides and bottom of bowl.
Add vanilla and mix well.
Managing Oven Real Estate
Preparing three 9-inch round pans simultaneously demands strategic oven placement. Stagger the pans across racks to ensure proper airflow, rotating them halfway through the 20 to 25 minute bake window. Parchment paper lining prevents sticking, which is critical when dealing with delicate layers containing cocoa and cake flour.
Sequencing the Batter
Creaming butter, oil, and granulated sugar for a full 3 minutes incorporates enough air to support the dense weight of the liquid colorants and buttermilk. Alternating the dry ingredients with the dairy prevents gluten overdevelopment, keeping the crumb tender. Acidic components like white vinegar react directly with baking soda to provide necessary lift.
Second-Day Texture Shifts
Leftovers improve over 24 hours as the crumb absorbs moisture from the rich cream cheese and butter icing. Store the frosted dessert chilled, but temper slices at room temperature for 30 minutes before serving to soften the butter content.