Preheat your oven to 350°F (175°C). Grease your pie dish.

In a mixing bowl, combine the flour, ¼ cup of sugar, and a pinch of salt. Whisk together.

Add the cold, cubed butter into the dry ingredients and work it in until it looks like coarse crumbs.

Stir in the egg yolk and add the cold water, one tablespoon at a time. Mix until the dough holds together.

Press the dough into the greased pie dish and bake for 15–20 minutes until lightly golden.

In a saucepan, combine the whole milk and ¾ cup of sugar. Heat until warm, but do not let it boil.

In a separate bowl, whisk the three large egg yolks and cornstarch until smooth.

Gradually whisk the warm milk mixture into the egg yolks.

Pour the mixture back into the saucepan and cook over medium heat, stirring continuously until thickened (about 5–7 minutes).

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

Pour the custard filling into the baked crust and spread evenly.

Bake for an additional 20–25 minutes until set and slightly jiggles in the center.

Allow to cool completely before slicing.