Mix all-purpose flour, unsweetened cocoa powder, baking powder, baking soda, and salt in a medium-sized bowl. Set it aside.
Place softened butter and sugar in a large bowl and mix with an electric mixer for 3-4 minutes or until lighter in color.Add room-temperature egg and egg yolk, one at a time, to the dough. Beat until incorporated.
Add vinegar, vanilla extract, and red food coloring. You want a bright red, so adjust the coloring amount as needed.
Add dry ingredients and mix just until combined. Cover the bowl with film paper and refrigerate for at least 2 hours.
Then, when ready to bake, preheat the oven to 375°F and line two baking sheets with parchment paper. Roll cookies into 1 ½ tablespoon-sized balls. Roll each ball in powdered sugar before placing on prepared pans. Then, roll each ball in powdered sugar one more time for the best coverage.
Bake cookies for 10-12 minutes or until the tops are puffy and the centers look shiny and just slightly wet. After removing the cookies from the oven, allow the cookies to cool on the pan for 3-5 minutes before transferring to a wire rack or plate to finish cooling.
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