Heat oil in a medium saucepan over medium-high heat; add onion and cumin seeds.
Sauté 2 minutes; add beans and tomato; sauté an additional 2 minutes. Add water and remove from heat. Using hand-held blender, process until desired consistency.
Stir in salt, cilantro and lime juice. Spoon into a small oven-safe bowl; sprinkle with cheese and broil 1 minute or until cheese is melted