1. In a skillet, heat oil over medium. Add carrots & sauté 5 minutes.
2. Add onion, celery & garlic.Sauté another 5 minutes or until vegetables begin to brown, stirring often.
3. Transfer cooked vegetables into a large stockpot. Add broth, lentils & undrained tomatoes. Bring to a boil.
4. Reduce heat to medium-low. Cover & simmer 35 minutes or until lentils are tender, stirring occasionally.
5. Season with pepper & vinegar. Ladle into soup bowls & serve.