Line two baking sheets with parchment paper and have a pastry bag with a plain tip ready.
Sift the powdered sugar and almond flour so there are no lumps. Scrape the inside of 1 vanilla bean and add with flour mixture.
In the bowl of a standing electric mixer, place the egg whites in and beat at 4 for 3 minutes. Add sugar and cream of tartar and beat for 3 minutes at 6. Up to 8 and beat for 3 more minutes or until stiff peaks. Add in flavoring or gels and beat for 1 final minute. Tip - you should be able to turn the bowl upside down without anything falling out)
Carefully fold the dry ingredients, in two batches, into the beaten egg whites with a flexible rubber spatula. When the mixture is just smooth and there are no streaks of egg white, stop folding and scrape the batter into the pastry bag (standing the bag in a tall glass helps if you’re alone).
Pipe the batter on the parchment-lined baking sheets in 1-inch circles (about 1 tablespoon each of batter), evenly spaced one-inch apart.
Tap the baking sheet a few times firmly on the countertop to flatten the macarons, then bake them for 15-18 minutes. Let cool completely then remove from baking sheet.