Heat the olive oil in a large pot or Dutch oven over medium heat. Add the chopped onion and cook until softened, about 5 minutes.
Add the minced garlic and cook for 1 minute until fragrant.
Pour in the crushed tomatoes and broth. Stir in the Italian seasoning, salt, and pepper. Bring the mixture to a simmer.
Add the refrigerated tortellini to the simmering soup. Cook according to package directions, usually 3 to 5 minutes, until the tortellini float and are cooked through.
Reduce the heat to low. Stir in the heavy cream until fully combined. Do not let the soup boil after adding the cream.
Stir in the grated Parmesan cheese until melted and the soup is smooth.
If using, stir in the fresh spinach until it wilts, about 1 minute.
Serve the soup hot.
Notes
For a richer flavor, use chicken broth instead of vegetable broth.
If you want a thicker soup, mix 1 tablespoon of cornstarch with 2 tablespoons of cold water, then stir this slurry into the simmering soup before adding the cream.
You can substitute fresh basil for the Italian seasoning for a brighter flavor.
Add cooked, shredded chicken breast for a heartier meal.