This pastry dough can be used as a base for many kinds of tarts and fruit pies.
Combine the flour and sugar in the bowl of a food processor. Pulse to combine. Add the butter or margarine and pulse for 15 more seconds.
In a small bowl, combine egg yolk and water. Beat lightly. Add egg to dough while pulsing, slowly and steadily until dough forms together.
Store dough in plastic wrap and flatten to a disc. Refrigerate for one hour before using.