Lemon Meringue Pie

I got this recipe from my Grandmother
She could make a pie in nothing flat.
This is a very old and good recipe.

Ingredients:
Lemon Filling:
4 egg yolks (reserve whites for meringue)
1/3 cup cornstarch
1 1/2 cups water
1 1/3 cups sugar
1/4 teaspoon salt
3 tablespoons butter
1/2 cup lemon juice
1 tablespoon finely grated lemon zest
1 (9-inch) pre-baked pie shell
1 recipe Meringue

Meringue Topping:
4 egg whites
1 pinch cream of tartar
2 tablespoons sugar
Place egg whites and cream of tartar
in the bowl of a stand mixer fitted
with the whisk attachment.
Beat egg whites until soft peaks form
and then gradually add sugar and
continue beating until stiff peaks form,
approximately 1 to 2 minutes.
Refrigerate until you use to top lemon filling.

Directions:
Preheat oven to 375 degrees .
In mixing bowl whisk egg yolks til thick,set aside.
In a medium saucepan, combine cornstarch,
water, sugar, and salt. Whisk to combine.
Turn heat on medium and, stirring frequently,
bring mixture to a boil.
Boil for 1 minute. Remove from heat,
Gradually, add hot mixture to egg yolks
and stir until you have
added at least half of the mixture.
Return egg mixture to saucepan,
turn heat down to low and cook,
stirring constantly, for 1 more minute.
Remove from heat and gently stir in butter,
lemon juice, and zest until well combined.
Pour mixture into pie shell
and top with meringue while
filling is still hot.
Make sure meringue completely covers
filling to the edge of the crust.
Bake for 10 to 12 minutes
or until meringue is golden.
Remove from oven to cool.