2Combine rice vinegar, sugar, and water in a saucepan. Bring to a boil over medium heat, stirring until sugar has dissolved, about 1 minute. Allow the mixture to cool.
3Place carrot, radish, and onion in a bowl. Pour in cooled vinegar mixture and let marinate at least 30 minutes. While vegetables marinate, set an oven rack about 6 inches from the heat source and preheat the broiler. Lightly oil a slotted broiler pan.
