Combine flour, sugar, salt, and lemon zest in a mixing bowl. Cut in butter until mixture resembles coarse crumbs. Mix in egg, egg yolk, and vanilla until dough forms. Wrap and chill for 30 minutes.

Heat milk and lemon zest in a saucepan until simmering. Whisk together sugar, flour, and egg yolks in a bowl. Gradually stir in hot milk. Return mixture to saucepan and cook until thickened, about 5-7 minutes. Remove from heat, stir in vanilla, and cool completely.

Preheat oven to 350°F (180°C). Roll out two-thirds of dough to line a tart pan. Pour cooled custard into pastry shell. Roll out remaining dough to cover custard and seal edges.

Sprinkle toasted pine nuts over the tart. Bake for 35-40 minutes until golden brown and filling is set.

Cool the tart in the pan for 30 minutes, then transfer to a wire rack to cool completely. Dust with powdered sugar before serving.