Make the crust. In a bowl, combine flour and salt. Cut in the cold butter with a pastry cutter or fingertips until pea-sized bits form. Sprinkle in ice water, 1 tablespoon at a time, until the dough holds together when pressed.

Chill and roll. Form into a disk, wrap, and chill 30 minutes. Roll on a lightly floured surface into a 12-inch circle. Fit into a 9-inch pie plate, trim, and crimp edges.

Blind bake. Prick the base with a fork. Line with parchment and fill with pie weights or dried beans. Bake at 400°F (200°C) for 15 minutes. Remove weights and parchment, bake 8–10 minutes more until golden. Cool on a rack.

Set up the lemon filling. In a medium saucepan, whisk sugar, cornstarch, and salt. Whisk in water until smooth. Cook over medium heat, stirring, until the mixture thickens and bubbles, 5–7 minutes.

Add lemon and eggs. Remove from heat. Whisk in lemon juice and zest. Slowly whisk a few spoonfuls of the hot mixture into the egg yolks to temper, then return the yolk mixture to the pan.

Finish the filling. Cook 2–3 minutes over low heat, stirring constantly, until glossy and thick. Remove from heat and stir in butter until melted. Pour filling into the warm crust.

Make the meringue. In a clean, grease-free bowl, beat egg whites and cream of tartar on medium speed until soft peaks form. Gradually add sugar, 1 tablespoon at a time, beating until stiff, glossy peaks form. Beat in vanilla.

Top the pie. Spread meringue over the hot filling, sealing all edges to the crust to prevent weeping. Create swoops and peaks with a spoon.

Bake to set. Bake at 350°F (175°C) for 12–15 minutes, until the meringue is golden on top. The peaks should be lightly browned.

Cool and set. Cool on a rack until room temperature, then chill at least 3 hours for clean slices. Use a sharp, damp knife to slice.