1Preheat an oven to 225 degrees F (110 degrees C). Whisk the cocoa powder and artificial sweetener together in a small bowl; set aside. Line a baking sheet with parchment paper.
2Beat egg whites and cream of tartar until foamy in a large mixing bowl. Add the vanilla, and beat until stiff peaks form. Lift your beater or whisk straight up: the egg whites should form a sharp peak that holds its shape. Fold in the cocoa powder mixture until evenly blended. Drop tablespoon-sized dollops of meringue onto the lined baking sheet.
3Bake in the preheated oven until the macaroons are crisp and dry, about 1 hour. Cool completely on a wire rack.
Footnotes
Cook's Note
If crispier meringues are desired, turn off the oven after one hour and let the meringues sit another 10 minutes before removing them.
Editor's Note
Be sure to use a sucralose- or stevia-based artificial sweetener. Other sweeteners lose their sweetness when cooked.