For tortilla soup like abuela used to make, start with zesty garlic chicken, add tomato sauce, and kick up the flavor when you top with avocado, cheese and cilantro.
While not nearly as sweet as bananas, plantains do have a sweet flavor. In this soup we keep that sweetness at bay by using firm plantains with green skins rather than riper brown-skinned ones--the sugars will have not yet developed, so the fruit will add starchy body to the soup without too much sweetness.