Start by spraying the air fryer basket or cooking pan with nonstick cooking spray, or brush with olive oil. Add the eggs, milk, pure vanilla extract, kosher salt, ground cinnamon, and allspice in a large mixing bowl.
Dip the bread slices into the batter, and let the bread soak for about 30 seconds so the bread fully absorbs the batter. Shake the bread to remove any excess batter. Place the coated bread into the air fryer basket or in the baking pan.
Air Fry at 320 degrees F for 6-8 minutes, flipping the bread halfway during cooking.
In a small skillet, add the butter, melt the butter over low-medium heat, add the brown sugar, and stir until the brown sugar is dissolved. Add the banana slices into the pan, then stir until the bananas are coated in the caramel sauce.
Place the French toast after it's cooked on a plate, spoon the banana mixture over the French toast, and add a sprinkle of ground cinnamon.