In a dutch oven, over medium-high heat, add ½ tablespoon avocado oil and Italian sausage. Cook until sausage is cooked through. Remove sausage from dutch oven and set aside. Discard excess fat from sausage.
Heat dutch oven over medium-high heat and add 1 tablespoon avocado oil. Add onion and garlic and cook until translucent, 4-5 minutes. Add tomato paste and cook for 1 minute. Add cooked sausage, dried oregano, and red pepper flakes (if using). Cook for 1 minute.
Add parmesan rind, crushed tomatoes, chicken broth, and 1 large fresh sprig of basil, and bring to a boil. Lower flame to medium and cook for 15 minutes.
Season with kosher salt and add freshly cracked pepper.
Lower to a simmer and slowly add heavy cream and stir to combine. Add tortellini and cook for 4-6 minutes or until tortellini are cooked al dente.
Turn off the flame and discard parmesan rind and basil sprig. Add spinach and stir until spinach is completely wilted. Ladle into bowls and top with freshly grated parmesan, chopped basil, and serve with crusty sourdough bread.