Dry roast the chilies, peppercorns, cumin, cardomom and cloves in a small skillet until cumin begins to pop. Let cool and grind in spice grinder. In blender or food processor, process garlic, ginger, one onion, spice mixture and vinegar to a paste. Put pork in a shallow bowl and marinate in paste for 1 hour. Heat oil in dutch oven and saute cinnamon stick for a few seconds. Add remaining onions. Cook for 2 minutes. Reduce heat to low, add 3 tablespoons of water. Cook until onions are golden brown about 20 minutes. Add cayenne and turmeric and stir for 20 seconds. Add meat and paste. Cook until meat is well browned. Add 1 cup of water and bring to a boil. Reduce heat, cover and simmer for 10 minutes. Add tamarind liquid and salt. Simmer for 40 minutes. Serve with rice.