Chilly weather demands a pot of soup on the stove. To enhance a simple lentil soup, first saute onion, carrot, and celery in olive oil for 10 minutes. Add a spoonful of cumin and coriander, then stir in 1 cup of crushed tomatoes. Simmer for 10 minutes before adding lentils and chicken or vegetables. Simmer again for 35 minutes.