In a large pot over medium-high heat, add the 1 pound ground Italian sausage and ½ cup diced onion. Cook for 5-7 minutes until the meat is no longer pink and the onion starts to soften. Add the 2 cloves minced garlic and cook for 1 minute.
Add the 3 tablespoons tomato paste, continue stirring, and cook for about 1 minute.
Add the 4 cups chicken broth, 1 (28-ounce) can crushed tomatoes, and 1 tablespoon Italian seasoning; cover and bring to a simmer. Cook uncovered until slightly reduced, about 10 minutes.
Stir in the 1 (25-ounce) bag frozen cheese ravioli, ½ cup heavy cream, ½ cup grated parmesan cheese plus more for sprinkling, and 2 cups baby spinach. Simmer for 2 more minutes to heat through and wilt the spinach.
Serve in bowls with a dollop of ricotta cheese on top, and a sprinkle of parmesan, if desired.
