Heat 2 tablespoons of olive oil in a large pot over medium heat. Add the diced onion and cook until translucent and fragrant, about 5 minutes. Stir in the minced garlic and sauté for another 1 minute, making sure not to let it burn.
Pour in 4 cups of vegetable broth and the entire can of diced tomatoes (with their juices). Stir in 1 teaspoon each of dried basil and oregano. Season with salt and black pepper to taste. Bring the mixture to a gentle boil, then reduce heat to a simmer.
Once the soup is simmering, add the cheese tortellini directly into the pot. Cook according to the package instructions, typically about 3 to 5 minutes, until the tortellini are tender and cooked through.
Stir in 2 cups of fresh spinach and 1/4 cup of chopped fresh basil. Let the spinach wilt in the hot soup for 1 to 2 minutes. Taste and adjust seasoning if needed.
Ladle the soup into bowls and top each serving with a generous sprinkle of grated Parmesan cheese. Serve immediately while warm and comforting.
