Heat oil in stock pot over medium high heat. Add onion, carrot, celery and red bell pepper; cook until onion begins to turn clear, about 5 minutes. Add lentils, garlic, cilantro, parsley and ground black pepper. Cook 1 more minute. Add vegetable broth. Bring to a boil; reduce heat to a simmer for 25 minutes, stirring occasionally or until lentils are tender.