In a food processor, combine the flour, sugar and salt. Add the butter and pulse until the mixture resembles coarse meal. Add 2 1/2 TBS water and pulse just until the pastry comes together; add more water if necessary. On a lightly floured surface, shape the pastry into a disk, wrap in plastic and refrigerate until chilled, about 30 minutes. Can be made ahead and refrigerated up to 2 days or frozen for one month.