1. 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.
2. Heat oven to 325 degrees F. Lightly grease two large baking sheets. Between two sheets of waxed paper, roll one disk to 1/4-inch thickness. Remove top sheet of waxed paper. Cut out cookies with a 2-1/2-inch star cookie cutter. Gather scraps and reroll. Repeat with remaining dough.
3. Bake 12 to 15 minutes, or until lightly browned. Cool cookies on baking sheets 5 minutes. Transfer to wire racks and cool.
1. To decorate, whisk together powdered sugar and lemon juice. Divide glaze into two bowls. Tint one portion of glaze yellow with food coloring. Working with one cookie at a time, spread either white or yellow glaze onto cookie. Using a toothpick, drag the alternate-color glaze through the wet cookie to make wispy designs. Dip edges into sugar crystals.