Preheat an air fryer to 350 degrees F. Butter a small oven-safe dish that will fit into the air fryer.

Combine apples, 2 tablespoons brown sugar, lemon juice, ½ teaspoon cinnamon, and salt in a small bowl. Mix to combine, then transfer the mixture into the prepared dish; cover tightly with aluminum foil.

Place the dish inside the basket and air fry for 10 minutes. Remove the foil and stir, then replace foil and air fry for another 5 minutes.

Meanwhile, in a clean bowl, combine remaining brown sugar and cinnamon, rolled oats, flour, and melted butter. Toss with a fork until large crumbles form.

When the 5 minutes is up, remove the foil and scatter the topping over the apples. Air fry for 5 minutes.

Serve with whipped cream, ice cream, or caramel sauce.