Place 1 teaspoon butter in an 8-inch baking dish, place in the air fryer, and heat at 300°F for 2 minutes, or until melted. Spread the butter around the baking dish.
In a medium bowl, combine apples, brown sugar, water, lemon juice, and cinnamon. Pour this mixture into the baking dish and cover with aluminum foil.
Bake in the air fryer at 350°F for 20 minutes or until fork tender. (you may need an additional 5-10 minutes depending on how fat your air fryer model cooks)
In a food processor, pulse oats, flour, brown sugar, and cold butter until the mixture is crumbly.
When the apples are finished baking, remove the foil from the baking pan and sprinkle on the topping.
Bake the apple crisp uncovered for 15 minutes at 350°F.
