Make the crust by mixing flour, powdered sugar, and salt. Cut in the cold butter until it resembles sandy crumbs. Add egg yolk and 1 tablespoon of cold water, mixing until it comes together. Press into a tart pan, prick with a fork, and chill for 15 to 20 minutes.

Preheat the oven to 350°F (175°C). Bake the crust for 18 to 22 minutes until lightly golden. Let it cool completely.

In a saucepan, whisk together sugar, cornstarch, and salt. Slowly whisk in the milk and cook over medium heat, stirring often until it thickens and bubbles. Temper the egg yolks with a little hot mixture, then return to the pot and cook briefly to set. Stir in butter and vanilla, then remove from heat.

Pour the filling into a bowl, press plastic wrap directly on the surface to prevent a skin, and chill until cool (about 1 to 2 hours).

Spoon the filling into the cooled crust and smooth it out. Top with fresh raspberries. If desired, warm the jam with water and lightly brush it over the berries for a glossy finish.