Mince garlic and finely chop enough onion to measure 1 cup. Cut enough kernels from cob to measure 1 1/2 cups.
In a small heavy saucepan with a tight-fitting lid, bring water to a boil with garlic, onion, cumin, coriander, and season with salt and pepper. Stir in rice and cook, covered, over low heat 15 minutes. Stir in corn and cook, covered, 3 minutes, or until water is absorbed and rice is just tender. Fluff mixture with a fork and transfer to a large bowl to cool completely.
Rinse and drain black beans. Stir cilantro into rice with beans, lime juice, and season salt and pepper.
Recipe courtesy of Gourmet Magazine