Slice the bananas into rounds about 1/2 inch thick.
Melt the butter by microwaving at 50% power for 30 seconds until almost melted, then stir.
Combine the brown sugar, cinnamon, and nutmeg in a medium bowl and mix well.
Add the banana slices and melted butter into the bowl and toss gently to coat evenly.
Place the banana rounds in a single layer in the air fryer basket using tongs.
Air fry at 375 degrees Fahrenheit for 4-5 minutes until tender and caramelized.
Serve immediately over toasted cinnamon swirl bread, pancakes, waffles, or with ice cream or yogurt topped with chopped walnuts.