1Heat oven to 350°F (325°F for dark or nonstick pans). Make, bake and cool cake as directed on box for two 8-inch or 9-inch round pans.
2To make orange-coconut filling, in small microwavable bowl, mix sugar and cornstarch. Gradually stir in 1/3 cup water. Stir in orange peel and orange juice. Microwave uncovered on High about 1 minute or until mixture thickens and boils; stir. Microwave 30 seconds longer, stirring every 15 seconds. Stir in 2 tablespoons coconut; cool.
3Fill cake layers with orange-coconut filling. Frost side and top of cake with frosting. Sprinkle 1/2 cup coconut over top. Store loosely covered.