Preheat your air fryer to 350°F (175°C).
Core and slice the apples into thin wedges, about 1/4 inch thick.
In a large bowl, combine the brown sugar, ground cinnamon, lemon juice, melted butter or coconut oil, and salt. Mix well.
Add the apple wedges to the bowl and toss until they are evenly coated with the cinnamon sugar mixture.
Place the apple wedges in a single layer in the air fryer basket. You may need to do this in batches depending on the size of your air fryer.
Air fry the apples for 10-12 minutes, shaking the basket halfway through, until they are tender and slightly caramelized.
Remove the apples from the air fryer and let them cool for a few minutes before serving.