Preheat oven to 200°C (400F). Grease a muffin pan with melted butter or baking spray and lightly dust with some cocoa powder or flour. Tap the pan and discard excess flour. You can also use a silicone (non-stick) muffin pan.
Sift and mix flour, cocoa powder, baking powder, salt, and baking soda in a medium-sized bowl and set aside.
Place butter and sugar in a large mixing bowl of a stand mixer fitted with the paddle attachment. Mix on medium speed until fluffy (around 2 minutes). Use a spatula to scrape any ingredients from the side of the bowl.
Add eggs, one by one, mixing well after each addition. Add vanilla extract and mix in red food coloring (liquid or gel). You'll need to add enough food coloring to achieve a deep red color (amount depends on the type of coloring used).
Add half of the dry ingredients, alternating with half of the buttermilk and mix on slow speed until just combined. Repeat for the remaining dry ingredients and buttermilk.
Divide the batter between 12 muffin pan cavities, filling ⅔ to ¾ of the way (do not overfill).
Bake for 5 minutes on 200°C (400F), then without opening the oven, decrease the temperature to 190°C (375F) and bake for another 12-18 minutes or until a skewer inserted into the center comes out clean.
Let the cakes cool in the muffin pan for 5-10 minutes, then transfer upside down (like an inverted muffin) to a wire rack (you may need to use a palette knife to scrape the edges from the side of the muffin pan). Let the cakes cool completely before glazing.