Preheat oven to 300°F. In a large braising pot over high heat, toast chiles until fragrant, about 2 minutes per side. Place in a small bowl and cover with hot water until submerged.

Season short ribs with salt and pepper. Heat oil in the same braising pot over high heat. Once oil is hot, sear short ribs until browned on all sides, about 2 minutes per side; transfer to a plate. Reduce heat to medium-low, add onions and garlic, and sauté until soft and translucent, about 5 minutes. Add soaked chiles with ½ cup of the soaking water, beef broth, vinegar, cumin and cinnamon. Stir and scrape the bottom of the pan with a wooden spoon to remove the browned bits of short rib. Transfer to a blender and puree until smooth. Return short ribs to the braising pot and pour the puree over them. Cover and place in the oven for 2 hours and 30 minutes.

Remove the meat from the bones, shred, return to the cooking juices and stir until coated.

Place chips on a large rimmed baking sheet. Top tortilla chips with short rib meat and cheese. Place under the broiler and cook until cheese melts and begins to bubble, about 3 minutes. Remove the nachos and top with avocado, tomato and cilantro. Serve with lime wedges, if desired.

Note: Short ribs can be made a day in advance and stored in the refrigerator. Reheat before making nachos.