In the bowl of a stand mixer fit with a paddle attachment, cream the butter and sugar until light and fluffy, about three minutes.
Turn mixer to high and add the egg. Scrape down the bowl and beat until well incorporated.
In a separate bowl mix together cocoa, vanilla and red food coloring to make a thick paste. Add to the batter, mixing thoroughly until completely combined. You may need to stop the mixer to scrape the bottom of the bowl, making sure that all the batter gets color.
Turn mixer to low and slowly add half of the buttermilk. Add half of the flour and mix until combined.
Scrape the bowl and repeat the process with the remaining milk and flour. Beat on high until smooth.
Turn mixer to low and add baking soda and white vinegar. Turn to high and beat a few more minutes.
Spoon batter into a paper lined cupcake baking pan and bake at 325 F for 20-25 minutes or until a skewer inserted into the center cupcake comes out clean.
Let rest in the pan for 10 minutes, then place them of a cooling rack to cool completely before frosting.