Preparation: In a mixing bowl, combine the rolled oats, water (or milk), half of the brown sugar, cinnamon, salt, and vanilla extract. Stir well until all the ingredients are thoroughly mixed.

Preheat the Air Fryer: Set your air fryer to 350°F (about 175°C). Some air fryer models don't require preheating, but it can help to ensure even cooking.

Transfer to a Dish: Pour the oatmeal mixture into an air fryer-safe dish. If you're concerned about sticking, lightly grease the dish with cooking spray or a bit of butter.

Cooking Time: Place the dish in the air fryer basket. Cook for about 15-20 minutes. The timing might vary depending on your air fryer model, so it's good to check at the 15-minute mark.

Add More Brown Sugar: Halfway through the cooking process (around 7-10 minutes in), carefully open the air fryer and sprinkle the remaining brown sugar over the top of the oatmeal. This will create that deliciously caramelized top layer.

Final Check: At the end of the cooking time, ensure that the oatmeal is cooked through and the top is nicely caramelized. If it's not quite there yet, you can cook it for a few more minutes.

Serve and Enjoy: Carefully remove the dish from the air fryer (it will be hot), let it cool for a minute, then add your favorite toppings like fresh fruits, nuts, a dollop of yogurt, or an extra sprinkle of brown sugar or cinnamon.