Preheat oven to 350°F (175°C).
In a mixing bowl, combine flour and salt. Cut in butter until mixture resembles coarse crumbs. Stir in ice water, a tablespoon at a time, until mixture forms a ball. Wrap in plastic and refrigerate for 4 hours or overnight.
Roll dough out to fit a 9-inch pie dish. Press dough evenly into the bottom and sides of the dish. Trim excess dough. Bake for 15 minutes or until golden brown. Let cool.
In a saucepan, whisk together sugar, flour, cornstarch, and salt. Stir in water and cook over medium-high heat until mixture comes to a boil and thickens. Remove from heat and stir in butter.
In a small bowl, whisk egg yolks. Gradually whisk in ½ cup of the hot sugar mixture. Return egg mixture to the saucepan. Bring to a boil and continue to cook while stirring constantly until thick. Remove from heat and stir in lemon juice and zest. Pour filling into baked crust.
In a large glass or metal bowl, whip egg whites and cream of tartar until foamy. Add sugar gradually and continue to whip until stiff peaks form. Spread meringue over pie, sealing the edges at the crust.
Bake in preheated oven for 10 minutes, or until meringue is golden brown. Cool before serving.