Mix Dry Ingredients: In a bowl, whisk flour, granulated sugar, baking powder, salt, and cinnamon.
Add Wet Ingredients: Create a well; pour in melted butter, milk, and vanilla. Stir until just combined.
Knead Lightly: Turn onto floured surface; knead 4–5 times. Pat into a ½‑inch thick rectangle.
Cut Bites: Slice into 1‑inch squares.
Preheat & Arrange: Preheat air fryer to 350 °F (175 °C). Line basket with parchment. Place bites in a single layer.
Air Fry: Cook at 350 °F for 8–10 minutes, flipping halfway, until edges are golden.
Coat in Butter: Transfer warm bites to a bowl, drizzle with melted butter, and toss gently.
Sugar Coat: Toss in cinnamon‑sugar mixture until evenly coated.
Optional Glaze: Whisk powdered sugar, vanilla, and 2 tbsp milk until smooth; thin with extra milk if needed. Drizzle over bites or serve on the side.