Optional: Fat-free plain Greek yogurt and minced fresh parsley
In a 6-qt. stockpot, cook and crumble sausage over medium-high heat until no longer pink, 5-7 minutes; remove with a slotted spoon.
In same pot, saute onion, celery and carrot until tender, 4-6 minutes. Add garlic and seasonings; cook and stir 1 minute. Stir in sausage, lentils, tomatoes and broth; bring to a boil. Reduce heat; simmer, covered, until lentils are tender, 30-40 minutes, stirring occasionally. Remove bay leaf.
Transfer 5 cups soup to a blender; cool slightly. Cover; process until smooth. Return to pot; heat through. If desired, top servings with yogurt and parsley. Freeze option: Freeze cooled soup in freezer containers. To use, partially thaw in refrigerator overnight. Heat through in a saucepan, stirring occasionally; add a little broth or water if necessary.