Heat oven to 350°F. In food processor, place flour, butter, powdered sugar and salt. Cover; process, using quick on-and-off motions, until dough forms a ball. Press dough firmly and evenly in bottom and up side of ungreased 10-inch tart pan with removable bottom. Bake 20 to 25 minutes or until lightly browned. Cool completely, about 20 minutes.