Preheat your oven to 375°F (190°C).

Rinse and dry the apples. Using an apple corer or a paring knife, remove the core of each apple, creating a hole about an inch in diameter, but make sure not to cut all the way through the bottom of the apple. You should have a small well in the center of each apple.

In a small bowl, mix together the brown sugar, cinnamon, and nutmeg (if using). If you'd like to add some crunch and extra flavor, you can also mix in the chopped walnuts or pecans and raisins or dried cranberries.

Stuff each apple with the sugar-cinnamon mixture, filling the hole and pressing down gently to pack the mixture in. You can adjust the amount of filling depending on the size of your apples and your personal preference.

Place the apples in a baking dish with high sides. Top each apple with a piece of butter.

Pour the boiling water into the bottom of the baking dish, being careful not to pour it over the apples. This will create steam to help the apples cook evenly and stay moist.

Place the baking dish in the preheated oven and bake for 45-60 minutes, or until the apples are tender but not mushy. The baking time will depend on the size and variety of your apples. Check for doneness by inserting a toothpick or knife into the apple; it should go in easily.

Remove the baking dish from the oven and let the apples cool for a few minutes before serving.