In a large skillet, sauté the onion and garlic together until tender. Add the lentils, chili powder, cumin, and oregano; stir together for a minute. Add the broth and bring to a boil.
Reduce the heat, and cover and simmer for about 30 minutes or until lentils are tender.
Stir in the salsa before serving with lettuce, tomatoes, and cheese.
Notes
1 tablespoon each of lettuce, tomatoes, and cheese used in nutrition calculation.