Whisk flour, sugar, and salt in a bowl.

Cut in the cold butter until the mixture looks like coarse crumbs.

Mix in the egg yolk. Add ice water one tablespoon at a time until the dough holds together when pressed.

Shape into a disk, wrap, and chill for 30 minutes.

Roll the dough and fit it into a 9-inch pie dish. Crimp the edges.

Line with parchment, fill with pie weights, and bake at 375°F until the edges look set. Remove weights and bake until lightly golden.

Whisk sugar, cornstarch, salt, and water in a saucepan.

Cook over medium heat, whisking, until thick and bubbling.

Whisk egg yolks in a bowl. Slowly whisk in a ladle of hot mixture to warm them.

Pour the yolk mixture back into the saucepan and cook for 1 to 2 minutes until thick.

Remove from heat and stir in butter, lemon juice, lemon zest, and vanilla.

Pour the hot filling into the baked crust.

Beat egg whites until foamy. Add cream of tartar and salt.

Beat to soft peaks, then add sugar slowly while beating.

Beat until glossy stiff peaks form. Beat in vanilla.

Spread meringue over the hot filling, sealing it to the crust edges. Create peaks with a spoon.

Bake at 375°F until the top is golden. Cool, then chill before slicing.