1. Prepare the Crust:

1. Preheat oven to 350°F (175°C). Grease a 9-inch tart pan with a removable bottom.
2. In a food processor, combine flour, sugar, salt, and butter. Pulse until mixture resembles coarse crumbs.
3. Add egg and vanilla extract. Pulse until dough comes together. Press dough into the tart pan, covering the bottom and sides. Chill for 30 minutes.
4. In a saucepan, heat milk over medium heat until steaming but not boiling. In a bowl, whisk egg yolks, sugar, cornstarch, and lemon zest until smooth.
5. Slowly pour the hot milk into the egg mixture, whisking constantly. Return mixture to the saucepan and cook over medium heat, stirring until thickened.
6. Pour custard into the chilled crust. Sprinkle pine nuts evenly over the top. Bake for 30-35 minutes or until golden brown.
7. Cool completely before dusting with powdered sugar. Serve at room temperature.