In a large saucepan, saute onion in oil until tender. Add garlic; cook 1 minute longer. Add the broth, lentils, chili powder and cumin. Bring to a boil. Reduce heat; cover and simmer for 20-25 minutes or until lentils are almost tender.
Stir in the corn, salsa, tomato paste, oregano and vinegar. Bring to a boil. Reduce heat; cover and simmer 10 minutes longer or until lentils are tender. Serve with rice; sprinkle with cheese.