1. Mix brown sugar and cinnamon. 2. Brush pineapple spears with melted butter. Sprinkle cinnamon sugar over the spears. 3. Place the spears into the air fryer basket in a single layer. Set fryer to 400°F for 10 minutes. Halfway through, brush with any remaining butter. 4. Pineapples are done when heated through and the sugar is bubbling.