Fill each core of an apple with 1 tablespoon brown sugar and 1/4 teaspoon cinnamon. Wrap each apple in a large piece of heavy foil (or a couple of pieces, just to be sure not to burn them). Place the apple in the coals of a campfire or barbecue grill and let cook for 5 - 10 minutes (we found 8 worked well). Remove and unwrap, being careful of the hot sugar.
I'm sure this would work in an oven as well.