You could substitute the canned tomatoes with a tomato paste/water mixture, but the flavor component will be different.
Thereafter, add 4 cups of fresh water (filtered or purified water is best; remember water is the main ingredient in soup so opt for the best quality).
Cook the ingredients for an hour (low flame) and serve! Add freshly grated Parmeggiono Reggiano.
Recipe by Scordo.com - Italian Food Recipes and Lifestyle at http://www.scordo.com/food/how-to-make-lentil-soup-homemade-soups-campbells-progresso-lenel.html