Heat olive oil in a large pot over medium heat.
Add chopped onion and sauté until translucent, about 5 minutes.
Stir in minced garlic and cook for another minute until fragrant.
Pour in the vegetable or chicken broth and diced tomatoes; bring to a simmer.
Add diced carrots and let the soup simmer for 5-7 minutes.
Stir in the tortellini and cook per package instructions, typically 3-5 minutes.
Add chopped spinach or kale and Italian seasoning; stir to combine.
Season with salt and pepper to taste before serving.