Preheat oven to 350°F (175°C).
In a mixing bowl, combine flour and salt for the crust. Cut in butter until mixture resembles coarse crumbs. Stir in ice water, a tablespoon at a time, until dough forms a ball. Wrap in plastic and refrigerate for 4 hours or overnight.
Roll out dough on a floured surface to fit a 9-inch pie dish. Transfer dough to pie dish. Trim and flute edges. Bake in preheated oven for 10-12 minutes or until golden brown. Let cool on a wire rack.
In a saucepan, whisk together sugar, flour, cornstarch, and salt. Stir in water, lemon juice, and lemon zest. Cook over medium-high heat, stirring frequently, until mixture comes to a boil. Stir in butter.
Place egg yolks in a small bowl and gradually whisk in ½ cup of hot sugar mixture. Whisk egg yolk mixture back into remaining sugar mixture. Bring to a boil and continue to cook while stirring constantly until thick. Remove from heat. Pour filling into baked pastry shell.
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 on a wire rack. Refrigerate for 1 hour before serving.