Preheat oven to 350 degrees. If making cupcakes: Line muffin pan with cupcake paper liners and spray nonstick spray into each one. If making a two layer cake: Butter two - 9 inch round cake pans and line the bottoms of the pans with parchment paper. Set aside.
In a medium mixing bowl, whisk (or sift) together the flour, salt, and, cocoa powder. Set aside.
In bowl of your stand mixer, or with a hand mixer, cream the butter and sugar together until light and fluffy (about 2-3 minutes).
Add the eggs, one at a time, beating well after each addition. Scrape down the sides of the bowl, as needed. With the last egg, add the vanilla and beat well till combined.
In a glass measuring cup or bowl, whisk the buttermilk with the red food coloring. Be careful not to splatter as the red color will stain.
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. This will ensure all the ingredients are combined well. Scrap sides of bowl as needed.
In a very small cup combine the vinegar and baking soda. Allow the mixture to fizz and then quickly fold, by hand, into the cake batter. (this would be a good step for kids to do as they’ll love the fizzy part)
To make cupcakes: fill each muffin cup about 2/3 to 3/4 fill. Bake for 15 minutes or until a toothpick inserted in the center of the cakes comes out clean. Let cool in pan for 5 minutes; then remove and cool on a wire rack completely before frosting.
To make a two layer cake: divide the batter evenly between the two prepared pans and bake in the preheated oven for 25 -30 minutes, or until a toothpick inserted in the center of the cakes comes out clean. Cool the cakes in their pans on a wire rack for 10 minutes. Place a wire rack on top of the cake pan and invert, lifting off the pan. Frost when cake is completely cool.