Preheat oven to 350 degrees F and line 24 muffin tins with paper liners. In a mixing bowl, combine flour, corn starch, cocoa powder, baking powder, baking soda, and salt.
In the bowl of a standing electric mixer, beat butter and sugar until light and creamy. Add in the eggs one at a time, beating to incorporate each. Mix in the sour cream, vanilla, and food coloring. Mix in the flour until just combined, scraping the sides of the bowl as needed.
Spoon batter into cupcake liners and bake for 15-18 minutes or until toothpick comes out with only a few crumbs or clean. Cool completely before adding frosting.