Preheat the oven to 375°F.
In a small bowl, combine the brown sugar, cinnamon, walnuts, and raisins.
Stuff the mixture into the apples, and place ½ tablespoon of butter on top of each apple.
Place the apples in a cast-iron skillet at least 2 inches apart. Pour the boiling water into the bottom of the pan to surround the apples.
Place the skillet in the oven and bake for 40 minutes, or until apples are cooked through but not mushy.
Spoon the juices from the skillet over the top of the apples. Put the apples in bowls and serve.