In a large mixing bowl, combine the diced apples, flour, sugar, baking powder, cinnamon, nutmeg, and salt. Stir to mix the dry ingredients evenly.
In a separate bowl, whisk together the milk, egg, vanilla extract, and melted butter until well combined.
Pour the wet ingredients into the dry ingredients and mix until just combined. Be careful not to overmix; a few lumps are okay.
Preheat the air fryer to 350°F (175°C).
Lightly spray the air fryer basket with cooking spray. Using a tablespoon, drop spoonfuls of the fritter batter into the basket, leaving space for the fritters to expand.
Air fry the fritters for 10-12 minutes, flipping them halfway through, until they are golden brown and cooked through.
If desired, prepare the glaze by mixing powdered sugar with milk until smooth and drizzle over the warm fritters once they are out of the air fryer.
Notes
For extra sweetness, drizzle with glaze after cooking.