Heat olive oil in a large pot over medium heat. Add the diced onion and sauté for 5 minutes until softened and translucent.
Stir in the minced garlic and cook for an additional minute until fragrant.
Add the can of diced tomatoes (with juice), vegetable broth, dried oregano, and dried basil. Bring the mixture to a boil, then reduce the heat and let it simmer for about 10 minutes.
Stir in the heavy cream (or coconut milk) and let the soup heat through without boiling, about 5 minutes.
Add the tortellini to the pot and cook according to the package instructions, usually about 5-7 minutes, until tender.
Stir in the chopped fresh basil and season the soup with salt and pepper to taste.
Serve hot, garnished with grated Parmesan cheese if desired.