In medium bowl, with electric mixer on medium, beat butter and sugar until light and fluffy. Beat in egg, corn syrup, lemon extract, and lemon rind until well-blended. Reduce mixer speed to low, and gradually beat in flour and salt. Gather dough into 2 balls; flatten each into a disk and wrap in plastic. Refrigerate dough at least 1 hour, or overnight. Set out dough briefly at room temperature to soften before rolling out.