Combine 5 tbsp butter, brown sugar, cranberries, pecans, orange zest, oats, cinnamon, and diced apple in a large bowl; set aside.
Shave a thin slice off the bottom of the remaining six apples so they sit flat. Cut top 1/2 inch off stem end of apples and reserve. Peel apples and use a melon baller or small measuring spoon to remove 1 2/-inch diameter core, being careful not to cut through the bottom of the apple.
Melt remaining butter in 12-inch ovensafe skillet over medium heat. Once foaming subsides, add apples, stem-side down, and cook until cut surface is golden brown, about 3 minutes.
Flip apples, reduce heat to low, and spoon filling inside, mounding excess filling over cavities; top with reserved apple caps.
Add maple syrup and 1/3 cup cider to skillet. Transfer skillet to oven, and bake 35-40 minutes, or until skewer inserted into apple meets little resistance. Baste even 10 minutes with maple syrup mixture in skillet.
Transfer apples to serving platter. Stir up to 2 tbsp remaining cider into sauce to adjust consistency. Pour sauce over apples and serve.