Mix lemon juice, olive oil, cilantro and salt in a small glass bowl and set aside. Bring reserved corn cooking liquid to a boil in small saucepan. Add quinoa and cumin; cover and simmer until quinoa absorbs the liquid and is tender (about 10 minutes). Transfer quinoa to a large glass bowl; cool slightly. Add corn, black beans, tomato, red onions and dressing. Toss to combine. Cover and chill for about 4 hours. Serves 4.
Recipe from the Frances Stern Nutrition Center at New England Medical Center, Boston.