1. In a large mixing bowl, beat cane sugar and butter with an electric mixer on medium until light and fluffy.
2. Add egg, lemon zest, and lemon juice. Beat on low speed until combined.  
3. In a medium bowl, whisk together flour, baking powder, and salt. Gradually add flour mixture to butter mixture, beating until combined.
4. Cover dough and refrigerate for 1 hour or until firm enough to roll out.  
5. Preheat oven to 350°F. Transfer half of cookie dough to a generously floured work surface. Return remaining dough to the refrigerator. Roll dough to ⅛- to ¼-inch thickness. Use cookie cutters to cut into desired shapes. Transfer to ungreased cookie sheets using a thin metal spatula or pancake turner. Brush any excess flour from cookie dough with a pastry brush. Repeat with remaining dough, rerolling scraps.   
6. Bake for 8 to 10 minutes or until edges of cookies are set and just starting to lightly brown. Transfer to wire racks and cool completely.  
7. For lemon icing, in a large mixing bowl, combine powdered sugar and cream of tartar. Add egg whites and lemon juice. Beat with an electric mixer on low until combined and then on high for 4 to 6 minutes or until icing is very thick. Add natural food coloring to the icing, if desired. 

Each cookie contains: 164 calories, 6 g fat, 4 g saturated fat, 0 g trans fat, 23 mg cholesterol, 50 mg sodium, 26 g carbohydrates, 0 g fiber, 17 g sugar, 2 g protein. Daily values: 4% vitamin A, 1% vitamin C, 1% calcium, 3% iron.