In a bowl, combine the flour, sugar, zest and salt.
Incorporate the soft butter, then the egg yolk. Do not work the dough too much, stop as soon as it is homogeneous.
Shape the dough into a ball, wrap it and leave it in the fridge for at least 1 hour.
Preheat oven to 200°C (400°F).
Grease 6 tartlet rings (or 1 large ring).
Roll out the dough on a floured surface. Cut out six pieces and fill the tartlet rings.
Bake the pastry for 15 minutes, filled with pie weights. Remove the weights and continue baking for another 5 minutes, or until the pastry is golden brown (if you make a large pie, the baking time will be a little longer).
Let the crusts cool on a wire rack before assembling.