In a Dutch oven, crumble the Italian turkey sausage and add the finely chopped onion. Cook over medium heat for 5-7 minutes until browned and translucent.

Stir in the minced garlic and sauté for an additional minute until fragrant.

Add the reduced-sodium chicken broth, water, and undrained diced tomatoes to the pot. Bring to a rolling boil.

Stir in the refrigerated cheese tortellini. Boil for 5-8 minutes, or until the tortellini floats and is nearly tender.

Reduce heat to low, then add chopped spinach, minced basil, pepper, and crushed red pepper flakes. Cook for 2-3 minutes until spinach wilts.

Ladle into bowls while hot, garnishing with shredded Parmesan cheese if desired.