Whisk the flour, powdered sugar, and salt in a bowl.

Cut in the cold butter until the mix resembles fine crumbs with pea-sized bits.

Stir in the egg yolk and vanilla, then drizzle in a tiny splash of ice water if the mixture looks dry.

Press the dough into two 4-inch tart pans with removable bottoms.

Prick the base with a fork and chill for 15 minutes.

Preheat the oven to 350°F (175°C) and bake the shells for 14 to 17 minutes until lightly golden.

Whisk the egg yolks, sugar, cornstarch, lemon juice, and lemon zest in a small saucepan.

Cook over low heat, whisking constantly, until it thickens and gently bubbles at the edges, about 3 to 6 minutes.

Remove from heat and whisk in the butter and cream until smooth.

Strain if desired, then spoon into the cooled crusts.

Chill for 1 to 2 hours until set and glossy.