Cook green pepper and onion in olive oil until softened, about 4 minutes. Add garlic, water, broth and lentils.
Bring to a boil and reduce heat to simmer. Cover and cook 25 minutes. Stir in remaining ingredients (except buns) and simmer an additional 10-15 minutes or until thickened.
Spoon lentil mixture over hamburger buns and serve.
