Preheat oven to 180 C.
Using a handheld mixer, beat 3 tbsp. unsalted butter, 1/4 cup sugar, 1/2 tsp. cinnamon, and 1/8 tsp. nutmeg together until combined. Stir in 1/4 cup rolled oats, then 2 tbsp. each of raisins, dried cranberries, and nuts. Set aside.
Using a sharp knife, cut around the core of 4 apples, about halfway or 3/4 down. Use a spoon to carefully dig out the core. Once the core is out, use a spoon to dig out any more seeds.
Place cored apples in a baking pan. Spoon fill each apple, filling all the way to the top. Pour 3/4 cup warm water into the pan around the apples (helps prevent them from drying out/burning).
Bake for 40-45 minutes or until apples appear slightly soft. Serve warm with salted caramel, whipped cream, or ice cream.