Preheat oven to 350 degrees. Line 2 cupcake tins with liners.
Pour buttermilk into a large measuring cup. Add food gel or coloring and whisk until fully combined and buttermilk is a deep red. Set aside.
1 cup buttermilk, 2 oz red food coloring
In a small bowl, add baking soda and vinegar, mix to combine and set aside.
1 teaspoon baking soda, 1 teaspoon white distilled vinegar
In a large bowl, sift the cake flour, cocoa powder, baking powder and salt.
2 ½ cups cake flour, 2 tablespoon cocoa powder, 1 teaspoon baking powder, 1 teaspoon salt
In the bowl of a stand mixer, add butter and sugar and beat on medium speed until light and fluffy, about 3 minutes.
1 stick unsalted butter, 1 ½ cups sugar
Add in the eggs, one at a time, followed by the vanilla.
2 large eggs, 1 teaspoon vanilla
With the mixer off, add ⅓ of the flour mixture and ⅓ of the buttermilk. Mix on low until fully combined. Add another ⅓ of each and once combined, add in the remaining ⅓ of each.
Add the baking soda and vinegar mixture and mix to combine.
Divide the batter between the cupcake pans, filling each cavity to ¾ full.
Bake for 20 minutes or until a toothpick inserted in the center comes out clean.
Cool cupcakes on a wire rack.