Preheat oven to 350ºF.

It is imperative that your mixing bowl be free of oil, and that the egg whites do not have any yolk in them.

Using a stand mixer or wire whisk, slowly beat together the egg whites with cream of tartar and vanilla. Slowly increase the speed and beat until soft peaks form, about one minute. Gradually add the sugar, one tablespoon or so at a time, beating continuously until stiff glossy peaks are formed.

Using a clean spatula, spoon a small amount of meringue all around the edge of the pie, making sure it touches the pie crust all around. Mound the remaining meringue in the center of the pie and spread so that filling is entirely covered, leaving it mounded in the center of the pie.

Bake pie for 20 minutes or until meringue just begins to brown. Cool completely before cutting, or the meringue will be watery.