Stir in chili powder and cook 1 minute, stirring constantly. Add lentils, tomatoes and remaining cups of broth. Bring to a boil, reduce heat to medium-low and simmer partially covered for 30 minutes or until lentils are almost tender. Uncover and cook for 10 minutes longer. Taste for flavor, add any salt or spices as needed. Stir in cilantro and serve.