Preheat the air fryer: Set it to 375°F (190°C) for 3–5 minutes so it’s hot when the bananas go in.
Prep the bananas: Peel and slice them into 1/2-inch thick rounds, or cut them lengthwise into halves or quarters if you prefer larger pieces.
Mix the coating: In a small bowl, stir together sugar, cinnamon, and a pinch of salt.
Brush and coat: Lightly brush the banana pieces with melted butter (or coconut oil) on all sides. Sprinkle the cinnamon sugar over them, turning to coat well.
Grease the basket: Lightly spray or brush the air fryer basket or tray to prevent sticking. Place bananas in a single layer with a little space between pieces.
Air fry: Cook for 5–7 minutes, flipping halfway.
They’re done when the sugar is caramelized and the edges look golden with slight crisp spots.
Serve: Let them cool for 1 minute to set the caramelized coating. Add any toppings you like and serve warm.