Combine pork seasonings and coat meat.
Place in Dutch Oven or roasting pan with ½ cup water and topped with sliced onions.
Cover tightly with foil or lid then place in oven at 275 degrees for 5-6 hours, or until fork tender. Remove from oven and let rest till cool enough to handle, then remove any large chunks of fat and shred meat (reserve juices).
Heat oil in large pot and sauté onions till translucent (5 mins).
Add garlic till aromatic(2 mins), then add tomatoes until softened (2 mins).
Add remaining ingredients, minus salt and pepper.
Stir occasionally for 30 mintutes.
Add shredded pork and pan juices to soup and simmer for 30 more minutes. Salt and pepper to taste.
Serve with shredded cheddar, lime wedge, chopped cilantro, and flour tortillas.