Prepare and bake one recipe of butter pie crust pastry. Seperate egg yolks and whites. Leave egg whites in a mixing bowl on counter so that it can come to room temperature.
Combine 1/3 cup sugar, cornstarch, salt, milk, and cream of coconut into a saucepan. Heat until thickened and bubbly.
Beat egg yolks in a seperate bowl, and add about one cup of the hot pudding mixture to the bowl. Combine immediately, and do not let the eggs curdle.
Add the egg yolk mixture back to the saucepan, and stir until combined. Cook for a few more minutes, and remove from heat.
Add butter and 2 teaspoons of vanilla to mixture. Stir until butter is melted, and then add one cup of coconut. Pour hot filling into baked pie shell.
Add remaining vanilla and cream of tartar to egg whites. Beat on high in the mixture until soft peaks form.
Add sugar, and beat on high until stiff peaks form.
Spread the meringue on top of the pie filling, and spread to edges. Seal meringue to edges of pie crust. Use a spoon to even out and make designs in the meringue. Sprinkle with flaked coconut if desired.
Bake in a preheated 350-degree oven for about 20 minutes or until the meringue has cooked and slightly browned.
Cool for one hour on a wire rack. Remove to refrigerator for 3 to 6 hours prior to serving.
Cover left over pie, and refrigerate for up to three days.