1. Combine flour, sugar, and salt in food processor; blend for 5 seconds. Add margarine and pulse until mixture is crumb-like.
2. Add 2 tablespoons whipping cream and yolk. Blend until moist clumps form, adding more cream by teaspoonfuls if dough is dry.
3. Gather dough into a ball; flatten into a disk. Wrap and chill 1 hour. (Dough can be made 2 days ahead. Keep in the fridge.)
4. Roll out dough on lightly floured surface to a 13-inch (33-cm) circle. Transfer to 9-inch (23-cm)-diameter tart pan with removable bottom. Pierce crust all over with fork; refrigerate 1 hour.
5. Preheat oven to 400°F (200°C). Bake crust until golden, about 20 minutes. Allow crust to cool completely.