In a skillet over medium heat, add chiles and roast, turning as needed, for about 20 to 30 seconds or until lightly browned.
Remove from pan and place in a bowl with enough hot water to cover. Soak for about 15 to 20 minute or until softened. Remove and discard stems.
In a blender, combine stemmed chiles, tomato, onion, garlic, vinegar, oregano, cinnamon, cloves, brown sugar, and salt and pepper to taste. Process until smooth and the consistency of a thick paste. Set aside.
In a thick-bottomed pot over medium heat, heat oil. Add pork and cook, turning as needed, until lightly browned. Remove and discard any excess oil from pan.
Add chili paste and stir together to fully coat the meat.
Add water and bring to a boil, skimming any scum that may float on top.
Lower heat, cover, and cook for about 1 1/2 to 2 hours or until meat is fork-tender. Season with salt to taste. Serve hot.
Add more water in 1/2 cup increments if the sauce is drying out before the meat is fully cooked and tender.