Cake: In a large bowl sift together the flour, salt, and cocoa powder. Set aside.
In mixing bowl, beat butter until soft. Add the sugar and beat until light and fluffy, about 3 minutes. Add the egg and beat until incorporated. Scrape down the sides of the bowl. Add the vanilla extract and beat until combined.
In a measuring cup, whisk the buttermilk with the red food coloring. With the mixer on low speed, alternately add the flour mixture and buttermilk to the butter mixture, in three additions, beginning and ending with the flour.
In a small cup combine the vinegar and baking soda. Allow the mixture to fizz and then quickly fold into the cake batter.
Working quickly, divide the batter evenly among the 12 muffin cups and smooth the tops with an offset spatula or the back of a spoon. Bake in an oven preheated to 350° for 18-23 minutes (until toothpick inserted in the center comes out clean.)
Frosting: Beat the cream cheese until smooth. Add vanilla and powdered sugar and mix until smooth. Gradually add the cream and whip until frosting is thick enough to pipe. Add more sugar or cream as needed to get the right consistency. Makes 12 cupcakes