Pre-bake the crust: Heat the oven to 375°F (190°C). Fit the crust into a 9-inch pie dish, prick the bottom with a fork, line with parchment, and fill with pie weights. Bake for 15 minutes, remove weights and parchment, and bake 8–10 more minutes until golden. Let cool slightly.

Set up the lemon filling: In a medium saucepan, whisk together sugar, cornstarch, and salt. Add water gradually while whisking to prevent lumps. Cook over medium heat, whisking, until it starts to bubble and thicken, 5–7 minutes.

Add lemon and yolks: In a small bowl, whisk the egg yolks. Slowly ladle in about 1/2 cup of the hot mixture to temper, whisking constantly. Return the yolk mixture to the saucepan. Cook 1–2 minutes, whisking, until thick and glossy.

Finish the curd: Remove from heat. Whisk in lemon juice, zest, and butter until smooth. Taste for balance—add a little more juice if you like it sharper. Keep warm over the lowest heat while you make the meringue.

Preheat for baking: Reduce oven to 350°F (175°C).

Make the meringue: In a clean, grease-free bowl, whisk egg whites with cream of tartar and a pinch of salt on medium speed until foamy. Mix sugar and cornstarch together in a small bowl. Increase mixer speed to medium-high and add the sugar mixture 1 tablespoon at a time. Beat until glossy, stiff peaks form. Beat in vanilla just to combine.

Assemble the pie: Pour the hot lemon filling into the warm crust. Immediately spoon the meringue over the filling, starting at the edges and sealing to the crust all the way around. Mound and swirl the top with a spatula for peaks.

Bake to set: Bake at 350°F (175°C) for 15–18 minutes, until the meringue is lightly browned with toasted tips. Avoid overbaking.

Cool gradually: Cool on a wire rack for 1 hour, then refrigerate uncovered for at least 3 hours before slicing. Wipe your knife between cuts for cleaner slices.

Serve: Enjoy chilled or slightly cool. The filling should be set and sliceable, with a tender, glossy meringue.