Preheat the oven to 350° F.
In a small saucepan stir together the Clabber Girl Cornstarch and the water. Bring to a boil, stirring constantly and then let cool slightly. With an electric mixer beat the egg whites until foamy. Add the cream of tartar and continue beating the meringue at medium speed, adding the sugar in a stream. Beat at high speed until it holds soft peaks. Add the vanilla and beat in the cornstarch mixture 1 tablespoon at a time, beating at high speed until the meringue holds stiff peaks.
Immediately spread the meringue on top of the pie, making sure the meringue is touching the crust all around. Spread it evenly making decorative spikes and swirls.
Bake the pie in the 350° F oven for 20 to 30 minutes or until the topping is browned. Let cool at room temperature before chilling.