Melt 1 cup sugar and cook until golden brown. Pour sugar into a 9x5 loaf pan or 3 inch deep, 9 inch round cake pan being sure to coat bottom well. Zest orange into long thin strips. Place in saucepan, cover with water and bring to a boil. Drain, refresh under cold water then drain again. Peel apples, halve and core. Cut into 1/8-inch thick slices. Keep neatly stacked. Using flat pieces only (discard round ends) place a layer neatly into bottom of loaf pan. Cover with another layer keeping as neat as possible. Press down to even them out. Sprinkle with a bit of sugar, then some zest. Repeat adding sugar and zest every 2-3 layer. Continue to build layer 3-4 inches above edge of pan keeping lines straight. Cover with plastic wrap then wrap entirely in aluminum foil. Place in a shallow tray to catch drippings. Let sit for 24 hours. Drain juice and unwrap pan. Drain excess juice and wrap in double layer aluminum foil. Place in a large deep roasting pan, fill pan ½ up the sides of pan with water. Bake at 300ºF for 5-6 ½ hours. It is done when it fills about ¾ of the mold, apples are dark brown and a knife passes easily through. Unwrap, cool and let chill for several hours. Slice thinly and serve.