First, cut your apples in half, then using a spoon, remove the seeds and remove a thin layer to remove the center core. You want to keep most of the apple intact, but create a bit of a "bowl" in each half for the filling to nestle into.
Place the apples in the air fryer, cut side up and bake at 325 for 10 minutes. After baking this first round, you should be able to pierce the apples with a fork, but they shouldn’t be super soft. If using large apples, you may need to add a minute or 2.
While the apples are baking, whip up the crisp topping. Add all ingredients to a bowl, then mix and work the butter into the ingredients until it comes together in large chunks, but is not a cohesive, smooth dough.
Once the apples have finished cooking, carefully and generously spoon on the crisp topping to each apple, gently packing it into the semi-hollowed center. Gently packing the crisp topping helps it stay in place during the cooking process.
Bake the apples again with the topping at 325 for 10 minutes. The topping should be crispy and golden, and the apples nice and soft.