Position racks in the upper and lower thirds of the oven; preheat to 250 degrees F. Line 2 baking sheets with parchment paper.
Beat the egg whites, cream of tartar and salt in a large clean dry bowl with a mixer on medium speed until foamy. Increase the speed to medium high and beat until thick and opaque, about 1 more minute. Gradually add the confectioners' sugar, about 1/4 cup at a time, and beat until stiff shiny peaks form, about 5 more minutes.
Transfer the meringue to a pastry bag fitted with a star tip. Pipe 1/2-inch drops that are just touching to form about twenty-four 2- to 3-inch cookies. Bake at 250 degrees F until dry and crisp, 3 to 4 hours. Let cool.