Tomato Tortellini Soup

We had this at my friend Leah's house one night and I fell in love with it! It's so easy and delicious and I'm so glad she decided to share the recipe! 

4  cups vegetable broth2 14.5-ounce cans diced tomatoes with basil, oregano and garlic, undrained1 ounce tomato sauce (but I used 8 ounces because I wanted to thicken up the broth, it worked and we liked it better)1 yellow onion , chopped1 1/2 teaspoons garlic, minced coarse salt and freshly ground pepper, to taste2  9-ounce packages fresh, cheese-filled tortellini1/4 cup Parmigiano Reggiano cheese, freshly grated

In a slow cooker, combine broth, diced tomatoes, tomato sauce, onion, garlic and salt and pepper. 
Cover and cook on low 5 -6 hours; add tortellini and cook on low for 20 additional minutes. If soup seems too thick, add water 1/2 cup at a time to thin. Garnish with cheese. Serve with Creamy Corn Muffins.