Mix flour, salt, sugar; cut in butter, add ice water to form dough. Chill 30 minutes.
Preheat oven to 375°F; roll dough, fit into 9-inch pie plate, bake with weights 15 minutes, then 10 minutes more. Cool.
Whisk sugar, cornstarch, salt, water, lemon juice, and zest; cook until thick. Add yolks, cook 2 minutes, stir in butter. Taste and adjust filling. Pour into crust.
Beat egg whites, cream of tartar to soft peaks; add sugar, vanilla, beat to stiff peaks. Spread over filling.
Bake at 350°F for 10–12 minutes until golden.
Cool 1 hour, chill 2 hours. Serve on a white ceramic pie plate with zest or berries.