Return meat to a simmer for about 2 hours or until almost done. Reheat the next day - taste and adjust seasonings. Thicken with regular or masa flour, your choice. A couple of tablespoons should be sufficient. Chop more onion and serve on the side.
Onions tend to lose their flavor when simmered for extended periods.
Grated Cheddar cheese and chopped cilantro may also be served on the side. Grind all herbs in a mortar if possible to release the essential oils.