Position the racks in the upper and lower thirds of the oven; preheat to 325 degrees . In a bowl, whisk the flour, cocoa powder, baking powder, salt and baking soda. In a small bowl, whisk the buttermilk, food color, vanilla and vinegar. In a large bowl, using an electric mixer at medium speed, beat the butter, sugar and brown sugar, occasionally scraping down the bowl, until light and fluffy, about 3 minutes. Add the eggs, 1 at a time, beating to blend between additions. Reduce speed to low; add the flour mixture and beat until just blended. Beat in the buttermilk mixture. Cover; refrigerate until firm, 2 hours.
Roll half the dough (keep the rest chilled) by the tablespoon into balls; roll in confectioners' sugar to thickly coat. Place 2 inches apart on 2 parchment-lined baking sheets.
Bake the cookies, rotating the sheets halfway through, until puffed and crinkled, 12 to 15 minutes. Let cool on the sheets 1 minute before transferring to racks. Using cooled sheets and fresh parchment, repeat with remaining dough.