Place room temperature egg whites and cream of tartar in a very clean bowl. Mix with clean, dry beaters until stiff. Add sugar gradually until stiff peaks form. Fold in flavoring such as grated lemon zest or ground cinnamon.
Place on a cookie sheet lined with parchment paper in teaspoon-sized circles, two inches apart.
Bake in preheated oven for 30 minutes, until centers are dry. Cookies should not be brown, but should come off of the sheet without sticking.