In medium bowl, mix ground almonds, flour, lemon peel, baking powder, cardamom and salt with whisk; set aside. In large bowl, beat butter with electric mixer on medium speed until creamy. Gradually add 1 cup powdered sugar; beat until light and fluffy. On low speed, beat in flour mixture just until blended. Divide dough in half. Cover with plastic wrap; refrigerate 1 hour or until firm.