I know there are better and more authentic recipes for this dish out there. (Share 'em if you've got 'em!) The only benefit of this one is that it's practically instant to make.
Mix equal parts canned black beans, rinsed and drained; canned corn, drained; and Ro-Tel (canned diced tomatoes and chile peppers). If desired, add lime juice and cumin. Chill until serving.