PLACE SAUSAGE AND WATER IN LARGE NONSTICK FRYING PAN; COVER TIGHTLY AND COOK OVER MEDIUM HEAT 8 MINUTES, STIRRING OCCASIONALLY. MEANWHILE CUT ONION INTO WEDGES. REMOVE SAUSAGE TO WARM PLATTER. POUR OFF DRIPPINGS. COOK AND STIR ONIONS AND APPLES IN 1 TABLESPOON OF THE BUTTER IN SAME FRYING PAN 4 MINUTES OR UNTIL APPLES ARE JUST TENDER. REMOVE TO SAUSAGE PLATTER. HEAT REMAINING TABLESPOON BUTTER, ADD POTATOES AND COOK, COVERED, OVER MEDIUM HIGH HEAT 5 MINUTES OR UNTIL POTATOES ARE TENDER AND GOLDEN BROWN, STIRRING OCCASIONALLY. COMBINE VINEGAR, SUGAR AND CARAWAY SEED. REDUCE HEAT; RETURN SAUSAGE, APPLE MIXTURE AND VINEGAR MIXTURE TO FRYING PAN AND COOK 1 MINUTE, OR UNTIL HEATED THROUGH, STIRRING GENTLY. SPRINKLE WITH PARSLEY.