I made a few changes to this soup after reading the reviews on Allrecipes.com. I will write the recipe below as it appears on Allrecipes, with my changes/additions in parentheses.
adapted from Allrecipes.com
1 onion, chopped
1/4 cup olive oil (about 1-2 Tbs)
2 carrots, diced
3 stalks celery, chopped
2 cloves garlic, minced (4 cloves)
1 tsp. dried oregano (1 1/2 tsp.)
1 tsp. dried basil (1 1/2 tsp.)
(small pinch of red pepper flakes)
1 14.5 oz. can crushed tomatoes (I didn't have a full can, so I substituted some tomato paste)
(1 can stewed tomatoes)
2 cups dry lentils
8 cups water
(1 Tbs. chicken bouillion)
1/2 cup spinach, thinly sliced (2 cups)
2 Tbs. vinegar (or red wine vinegar)
salt and pepper to taste
In a large soup pot, heat oil over medium heat. Add onions, carrots, and celery; cook and stir until onion is tender.
Stir in garlic, bay leaf, oregano, basil, and crushed red pepper; cook for 2 minutes.
Stir in lentils, and add water and tomatoes. Bring to a boil. Reduce heat, and simmer for at least 1 hour.
When ready to serve, stir in spinach, and cook until it wilts. Stir in vinegar, and season to taste with salt and pepper.