1. Cream margarine and sugar in a large mixing bowl until light and fluffy.
2. Add the eggs, and lemon rind, juice, and extract. Continue beating until light-colored.
3. Add the flour and salt and mix just until blended.
4. Form into logs and chill for several hours or overnight.
5. Preheat oven to 375 degrees Fahrenheit. Slice dough into 1/8-inch thick slices and place one-and-a-half inches apart on lined and greased cookie sheets.
6. Bake eight to 10 minutes or until lightly browned around the edges. Cool on wire racks.
7. Ice with some royal icing, if desired.