Let egg whites stand at room temperature for 30 minutes. Line a very large cookie sheet (or two smaller cookie sheets) with parchment paper or foil; set aside. In a small bowl, stir together sugar, cornstarch, and cardamom; set aside.

Preheat oven to 300 degrees F. In a medium bowl, combine egg whites, vanilla, and cream of tartar. Beat with an electric mixer on high speed until soft peaks form (tips curl over). Gradually add the sugar mixture, 1 tablespoon at a time, beating on high speed until stiff peaks form (tips stand straight). Fold in citrus peel.

Spoon egg white mixture into a piping bag fitted with an extra-large star tip. Pipe mixture into thirty swirls onto prepared cookie sheet, making each swirl about 2 inches in diameter and 1-1/2 inches tall and leaving a 1-1/2-inch space between swirls. (Or spoon egg white mixture into a resealable plastic bag. Snip off one corner. Pipe into thirty "kiss" shapes that are the same size as the swirls.)

Bake for 20 minutes (if using two cookie sheets, bake at the same time on separate racks). Turn off oven. Let cookies dry in oven, with door closed, for 30 minutes. Remove from oven and gently peel off the parchment paper or foil. Makes 30 servings.

Layer cookies between waxed paper in an airtight container; cover. Store at room temperature for up to 3 days or freeze for up to 3 months.

We do not recommend using sugar substitute for this recipe.