Prepare the apples:
Preheat your oven to 350°F (175°C). Core the apples using a melon baller or small spoon, leaving the bottom intact to hold the filling. Place the cored apples in a lightly greased baking dish.
Make the filling:
In a small mixing bowl, combine the oats, brown sugar, cinnamon, nutmeg, salt, and chopped nuts (if using). Stir in the raisins or dried cranberries if you like a touch of sweetness. Add the butter and toss the mixture until it’s evenly combined.
Stuff the apples:
Spoon the oat mixture into the center of each apple, pressing gently to pack it in. If you like a little extra sweetness, drizzle a bit of honey or maple syrup over the top of each stuffed apple.
Bake the apples:
Cover the baking dish with aluminum foil and bake for 25 minutes. After 25 minutes, remove the foil and bake for an additional 15-20 minutes, or until the apples are tender and the filling is golden brown.
Serve:
Let the baked apples cool slightly before serving. You can enjoy them as-is or with a dollop of whipped cream, vanilla yogurt, or a scoop of vanilla ice cream for an extra indulgence.