Preheat the air fryer to 390°F (200°C).
In a small bowl, whisk together maple syrup, cinnamon, nutmeg, and salt until smooth. Set aside.
Starting with half a small sugar pumpkin (or a whole one, if doubling), cut it in half from stem to base and scoop out the seeds.
Slice the pumpkin into vertical wedges, about 1 inch thick. Leave the skin on. Place in a mixing bowl
Pour over the butter followed by the maple syrup mixture.
Arrange slices in the air fryer basket in a single layer. Cook in batches if needed.
Air fry at 390°F for 13–15 minutes, flipping halfway through, until the slices are fork-tender and caramelized at the edges.
If desired, brush again with leftover maple butter and garnish before serving.