In a large pot, heat olive oil over medium heat. Add chopped onion and cook for 4-5 minutes until softened. Add minced garlic and cook for 1-2 minutes until fragrant.
Pour in broth, heavy cream, and diced tomatoes (with juice). Stir in dried basil, oregano, salt, and pepper. Bring the mixture to a gentle simmer.
Add tortellini to the pot and cook according to package instructions, usually 5-7 minutes for fresh or 8-10 for frozen, until tender. In the last 2 minutes, add spinach, stirring until wilted.
Stir in Parmesan until melted and well incorporated, adjusting seasoning as needed.
Ladle into bowls, garnish with fresh basil if desired, and serve hot.
