Preheat your oven to 350°F (175°C). Line two baking sheets with parchment paper.
In a bowl, whisk together the flour, cocoa powder, baking soda, and salt. Set aside.
In another bowl, cream together the butter and sugar until fluffy. Add eggs one at a time, mixing well after each. Mix in the vanilla and red food coloring.
Gradually add the dry ingredients to the wet mixture, alternating with the buttermilk, beginning and ending with the dry ingredients.
Drop tablespoons of dough onto the prepared baking sheets, spacing them about 2 inches apart.
Bake for 10 minutes or until the edges are set. Allow cookies to cool on the baking sheet for 5 minutes before transferring to a wire rack.
Notes
You can add cream cheese frosting between the cookies to make them sandwich cookies.