In a large resealable plastic bag, combine the flour, salt and pepper. Add pork chops and shake to coat. In a skillet, brown the chops on both sides in butter. Transfer to a greased 13-in. x 9-in. baking dish. Add water to dish. Place onion over chops. Cover and bake at 350° for 20 minutes.
Meanwhile, in a saucepan, combine the pineapple juice, brown sugar and mustard. Bring to a boil. Reduce heat; simmer, uncovered, for 10 minutes. Pour over pork. Bake, uncovered, for 5-10 minutes or until meat juices run clear. Yield: 6 servings.