Tip: If you don't have a microplane or zester, don't skip the zest. Instead, use a vegetable peeler to take just the orange part of the skin off the fruit. Leave behind as much of the white pith as possible. Then stack the strips and mince them with a sharp knife.
Sugar Substitute: Use Splenda Sugar Blend for Baking. Follow package directions to use 6 Tbsp. equivalent for filling and 1/2 cup equivalent for crust. Omit powdered sugar garnish.
To make ahead: Let bars cool completely, then layer in a container or sealable bag between sheets of parchment paper. Refrigerate for up to 1 day or freeze for up to 4 months. To serve from frozen, place on a platter and let thaw for 1 hour.
Equipment: 9x13-inch baking pan, parchment paper