In a 6 or 7-quart slow cooker, combine carrot, onion, celery, tomatoes, broth, bay leaf, basil, pepper, garlic powder, and salt. Stir to combine.
Cover and cook on high for 5 hours (or low for 8 hours). Uncover and carefully remove bay leaf.
Blend until smooth using a hand-held immersion blender. You can do this right in the crockpot. If you don’t have an immersion blender, you can also puréethis in batches in a traditional blender (be very careful!).
Add tortellini and continue to cook on high for 15 minutes or until tortellini is cooked through.
Stir in half & half and fresh basil; serve immediately, topped with additional fresh basil and Parmesan cheese, if desired.
Video
Notes
If desired, omit half & half, or replace it with heavy cream.
If you're not a fan of tortellini, the tomato soup is delicious without it. You could also add a can of white cannelini beans, rinsed and drained. They can be puréed into the soup, if desired.
Storage: Soup can be refrigerated for up to 3 days; it can be frozen for up to 3 months. For best results, omit the half & half before freezing; add it when you reheat the soup.