Preheat oven to 350º. Put paper liners in three 12 count muffin tins.
Whisk flour, cocoa and salt together in bowl.
Beat oil and sugar in an electric mixer on medium till well blended. Beat in eggs, one at a time. Lower mixer speed to low (you don’t want any splashing!), and carefully add the red food coloring. Add vanilla, then alternate flour with buttermilk, starting with half the flour, then half the buttermilk, the rest of the flour, then ending with buttermilk. Scrape down the bowl, then mix just briefly till combined.
Place baking soda and vinegar in a dish and stir to combine. Add to batter with mixer running. Beat for just 10 seconds.
Fill cupcake liners 2/3 full and bake 25-30 minutes or till cake tester comes out clean. Let cool slightly, then remove from pans. Cool completely before icing.
For frosting, beat cream cheese, butter and vanilla just till blended. Add powdered sugar slowly (2 cups at a time) and beat till frosting is smooth and at the correct consistency. You may find you prefer more or less powdered sugar than called for. Makes 4 cups.