Prep the apples: Peel the apples if you prefer (peels on is fine). Slice them into 1/2-inch rings. Use a small round cutter or a knife to remove the core from each slice to create “donuts.” Pat dry with paper towels.

Preheat the air fryer: Set to 350°F (175°C) and let it heat for 3–5 minutes. Lightly spray the basket with oil to prevent sticking.

Make the batter: In a bowl, whisk flour, sugar, baking powder, baking soda, salt, and cinnamon. In another bowl, whisk buttermilk, egg, vanilla, and melted butter. Add wet to dry and stir until just combined. The batter should be thick but dip-able. If too thick, add a splash of buttermilk.

Dip the apple rings: Working one at a time, dip each apple ring into the batter, letting excess drip back into the bowl. Use a fork to lift and a finger or second fork to scrape off extra so you don’t end up with gloopy rings.

Arrange in the basket: Place battered rings in a single layer with space between. Don’t crowd—work in batches for even crisping. Lightly mist the tops with oil spray for extra color and crunch.

Air fry: Cook 6–8 minutes, flip carefully, then cook another 4–6 minutes until golden and set. Timing varies by air fryer, so check at the 5-minute mark.

Coat in cinnamon sugar: Mix 1/2 cup sugar and 1 teaspoon cinnamon in a shallow bowl. While rings are still warm, lightly brush with melted butter (optional) and toss in the cinnamon sugar. Repeat with remaining batches.

Serve: Enjoy warm as is, or drizzle with a simple glaze (powdered sugar + a splash of milk + vanilla) for extra sweetness.