Preheat your air fryer to 375° F (190° C).
Wash and dry the apples. Then, peel and core the apples. From there, chop the apples into even-sized small pieces.
Add the chopped apples to a large bowl. Then, add the vanilla extract, lemon juice, sweetener, cinnamon, nutmeg, and salt to the bowl. Thoroughly mix to coat the apples.
Lightly spray a heat-safe ramekin with oil and pour the apple mixture into the ramekin. Place the ramekin in the air fryer basket and air fry the apples at 375° F for 12-14 minutes. Mix the apples halfway through. Make sure the apples are cooked, but not burnt.
While the apples cook, add the quick oats, sweetener, cinnamon, salt, and light butter to a bowl. Use a fork to combine the oat topping.
Pour the oat topping over the ramekin with the cooked apples. Then, air fry at 375° F for another 5-7 minutes or until the topping is crispy and golden brown. Check on it to make sure it doesn’t burn.
Very carefully remove the ramekin from the air fryer. Wear oven mitts because the ramekin will be very hot. Then, serve this apple crisp warm, and enjoy!