Mix flour, salt, and butter until crumbly. Add ice water gradually to form dough. Chill for 30 minutes, roll out, and line a 9-inch pie dish. Bake until lightly golden.
In a saucepan, whisk together sugar, flour, cornstarch, and salt. Gradually stir in water, lemon juice, and zest. Cook over medium heat until thickened. Stir in butter, then whisk in the egg yolks slowly. Pour hot filling into baked crust.
Beat egg whites with cream of tartar until soft peaks form. Add sugar gradually and continue beating until glossy stiff peaks form.
Spread meringue over hot filling, sealing edges to crust. Bake at 350°F (175°C) for 10-12 minutes, until golden.
Let the pie cool at room temperature for 2 hours. Slice and serve chilled or slightly warm.