Spinach Tortellini Tomato Soup

By: Diethood


2 tablespoons olive oil
1 tablespoon butter
1 yellow onion, chopped
3 cloves garlic, finely chopped
2 cans (14.5-ounces each) Italian Diced Tomatoes with Basil, Garlic and Oregano
4 cups tomato sauce
4 cups vegetable broth
1 package (12-ounces) frozen tortellini
1 bag (10-ounces) fresh baby spinach
salt and fresh ground pepper, to taste