Pack the ice cream firmly in the pie shell and refreeze at once.
Beat the egg whites with the salt until almost stiff.
Add the cream of tartar and then gradually beat hi the sugar until the meringue is very stiff.
Stir in the vanilla.
Spread the meringue over the ice cream carefully, making sure there are no gaps or holes, and that the meringue is in contact with the edge of the pie shell all around.
Bake in a hot oven, 450°, 4-5 minutes, or until the meringue is a delicate brown.
Serve at once.