In a large pot, combine the water, vinegar, brown sugar, cumin, cardamom and cayenne. Add the onion, 2 tablespoons of freshly ground pepper and 1 tablespoon of salt and bring to a boil over high heat. Reduce the heat slightly and simmer for 20 minutes. Add the short ribs and simmer over moderately low heat until the meat is just tender, about 2 hours. Let the ribs cool in the broth, then transfer them to a large platter. Discard the broth. Cover the ribs and refrigerate until the meat is firm, at least 3 hours.