1. Prepare stuffing mix according to package directions.
2. Cook sausage in a large skillet over medium-high heat, stirring often, 8 to 10 minutes or until meat crumbles and is no longer pink. Remove sausage from skillet with a slotted spoon, reserving drippings in skillet. Drain sausage on paper towels.
3. Stir together lemon juice and 1/4 cup water.
4. Cut apples in half, cutting through stem and bottom ends. Carefully scoop out apple pulp and cores into a bowl, leaving a 1/4-inch shell. Rub lemon juice mixture evenly onto cut sides of apple shells. Remove and discard seeds and cores from apple pulp; chop pulp.
5. Sauté onion and apple pulp in hot drippings over medium-high heat 6 to 8 minutes or until liquid evaporates and onion is tender.
6. Stir together stuffing, apple mixture, sausage, and parsley in a large bowl. Spoon stuffing mixture evenly in apple shells (about 1/2 cup stuffing per apple shell). Place apples in a 13- x 9-inch baking dish, and pour 1 cup cider vinegar around apples in dish.
7. Bake at 350° for 30 to 40 minutes or until apples are tender. Garnish, if desired. Serve immediately.
Note: For testing purposes only, we used Stove Top Cornbread Stuffing Mix.