Combine olive oil and butter in a large soup pot or Dutch oven; set it over medium heat and cook until the butter is melted.
Add onions; cook for 3 to 4 minutes or until translucent. Add garlic and continue to cook for 20 seconds or until fragrant.
Increase heat to medium-high and stir in the canned diced tomatoes and the tomato sauce; bring to a boil.
Add vegetable broth and bring to a boil. Stir in the frozen tortellini and baby spinach.
Season with salt and pepper and continue to cook over medium-high heat, stirring occasionally, for 10 minutes, or until tortellini is tender and soup is heated through.
Nutritional info is an estimate and provided as courtesy. Values may vary according to the ingredients and tools used. Please use your preferred nutritional calculator for more detailed info.