Mix flour and 1/4 teaspoon salt in medium bowl. Set aside. Beat butter and granulated sugar in large bowl with electric mixer on medium speed until light and fluffy. Add egg, egg yolk, lemon peel, lemon juice and food coloring, if using. Mix well.
Gradually beat in flour mixture on low speed until well mixed. Divide dough in half. Form each half into a log about 9 inches long and 1 1/2 inches in diameter. Wrap in wax paper. Refrigerate 1 hour or until firm.
Preheat oven 350°F. Cut dough into 1/4-inch thick slices. Place on ungreased baking sheets.
Bake 12 to 15 minutes or until very lightly browned around edges. Cool on baking sheets 1 minute. Remove to wire racks; cool completely.
Dip bottom of each cookie into glaze, then gently set cookie with the dipped bottom side up, onto a wire cooling rack to allow glaze to set up.
Mix 1 cup confectioners’ sugar, and lemon juice. Stir until well combined and smooth. If a thinner glaze is desired, add more lemon juice, a teaspon at a time. If a thicker glaze is desired, add more powdered sugar, a tablespoon at a time. Mix utnil smooth.
I find sprinkling a touch of flour onto the dough helps make it easier to form into a log.