Heat extra virgin olive oil over medium heat in 5 qt pot. Add chopped onions, carrots, celery, and garlic and cook until onions are translucent (about 10min). Stir occasionally.
Add bone broth, tomatoes, beans, chopped sweet potato, pepper, salt, Italian seasoning, fennel, red pepper flakes, and lentils. Stir to blend. Add parmesan rind. Cover and turn heat up to bring to simmer. Lower heat to keep at simmer and continue to simmer 10 min covered. Remove cover and simmer 10-20 more minutes until lentils are desired tenderness. Remove parmesan rind. Add basil and spinach and stir until wilted.
Serve topped with grated parmesan and basil sprigs if desired.
Notes
For a lighter meal, just add a piece of crusty sourdough bread or corn muffins and/ or a green salad.
For a more substantial meal, add a heartier sandwich.
Nutrition Facts were calculated without optional toppings.
To make this vegetarian/vegan, you can switch the bone broth for vegetable stock and omit the optional parmesan rind. This will still give you a delicious soup, but it will be a bit thinner with less flavor depth.