Place egg whites in a medium bowl. Let stand at room temperature for 30 minutes. Preheat oven to 300 degrees F. Line two large baking sheets with parchment paper or foil. Draw six 3-1/2-inch circles on each sheet of paper or foil. Set aside.
Add cream of tartar and salt to egg whites. Beat with an electric mixer on medium speed until soft peaks forms (tips curl). Gradually add the 1/2 cup superfine sugar, 1 tablespoon at a time, beating on high speed until stiff peaks form ( tips stand straight) and sugar is nearly dissolved.
Transfer meringue to a decorating bag fitted with a 3/8-inch round tip. Pipe snowflake shapes on top of circles on paper or foil. Sprinkle with the decorating sugar.
Bake all of the meringues at the same time on separate oven racks for 10 minutes. Turn off oven; let meringues dry in oven with door closed for 1 hour. Lift meringues off paper or foil. Transfer to wire racks; cool completely. Makes 12 meringue snowflakes.