01 - Preheat oven to 350°F (180°C).
02 - Wash and core the apples, leaving the bottom intact to form a cavity for the filling.
03 - Combine rolled oats, brown sugar, chopped walnuts, ground cinnamon, ground nutmeg, and salt in a mixing bowl.
04 - Fill each apple cavity with the oat mixture and top with cubed butter.
05 - Place stuffed apples upright in a baking dish and pour apple juice or water into the dish's base.
06 - Bake for 30 to 35 minutes until apples are tender but hold their shape.
07 - Serve warm, optionally accompanied by vanilla ice cream or whipped cream.