Preheat oven to 350 degrees Fahrenheit. Rinse the apples. Remove the core of the apples, and place the apples standing up in a buttered baking dish. With a knife, make 4 small incisions in the apple’s skin at the top of the apples (so the skin won’t burst in the oven). Put a cube of butter in the empty space where the core once was, in each apple. Sprinkle 1 tablespoon of sugar over each apple.