Put flour, sugar, salt in food processor and pulse to combine.

Scatter butter over dry ingredients and pulse until butter is coarsely cut in.

Stir yolk to break it up and add it a little at a time, pulsing after each addition. When egg is in, pulse 10 second pulses until dough forms clumps and curds.

Turn dough out onto cutting board and lightly knead the dough just until mixed.

Butter 9 inch tart pan with removable bottom. Press dough evenly over bottom and up sides. Save a small piece of dough in fridge to patch cracks after crust is baked. Freeze crust at least 30 min before baking.

Preheat oven to 375°F. Butter shiny side of aluminum foil and fit foil, buttered side down, tightly against crust. Put tart pan on baking sheet and bake 25 min. Carefully remove foil. If crust has puffed, press down gently with back of a spoon.

*for partially baked crust, patch crust if necessary and transfer to cooling rack in pan.

*for fully baked crust, bake another 8 min or so, until firm and golden brown. Transfer to rack and cool before filling. If you have to patch cracks, path with thin pieces of fridge dough and bake another 2 min.