Beat egg whites until frothy, sprinkle in cream of tartar and salt, and beat until stiff.
Beat in the sugar, 2 tablespoons at a time.
The mixture should be glossy and stand in stiff peaks when all the sugar has been added.
With the back of a tablespoon, spread meringue in a large, well-greased pie pan, pushing it high on the sides so that it resembles a pie shell.
Bake in a slow oven (300°) for 40 minutes.
Cool on a rack.