Combine flour, butter, sugar, egg, egg yolk, vanilla, and salt in a mixing bowl. Mix until coarse crumbs form. Wrap in plastic wrap and refrigerate for at least 30 minutes.

Heat whole milk in a saucepan until just steaming. In another bowl, whisk egg yolks, sugar, cornstarch, and lemon zest. Gradually pour hot milk into egg mixture, whisking continuously.

Return mixture to saucepan over medium heat. Stir constantly until the custard thickens, about 5-7 minutes. Remove from heat and stir in butter.

Transfer custard to a bowl, cover with plastic wrap directly on the surface. Cool at room temperature for 30 minutes, then refrigerate until fully chilled.

Preheat the oven to 350°F (175°C). Ensure the rack is in the center position.

Roll out chilled pastry dough on a floured surface to ¼ inch thick. Use a rolling pin to transfer to tart pan and press into edges.

Grease tart pan and line with rolled-out pastry, trimming excess. Prick the base with a fork.

Spread cooled custard into pastry shell, smoothing the top.

Sprinkle pine nuts or sliced almonds over the custard.

Bake in the preheated oven for 30-35 minutes, until the top is golden and custard is set.

Remove tart from oven, cool in the pan for 30 minutes, then transfer to a wire rack to cool completely.

Before serving, dust the tart with powdered sugar.