1. Saute onion, carrots, celery and garlic in oil until translucent, about 5 - 7 minutes.
2. Add lentils, water and tomatoes, and bring to a boil. Reduce heat and simmer, covered, for 25 minutes.
3. Add potatoes, sausage and spices and simmer, covered, for another 20 minutes or until lentils and potatoes are tender.