Mix flour, sugar, salt; cut in butter; add yolk & water; chill 30 mins.
Roll dough thin, cut circles, press into pans.
Line with parchment & weights, bake 12 mins + 5–8 mins until golden.
Whisk eggs, lemon juice, sugar, cornstarch; cook until thickened.
Remove heat, stir in butter & zest, strain, cool.
Fill cooled shells with curd, smooth tops, chill 2 hrs.
Unmold, dust sugar, garnish as desired.