Preheat the air fryer to 375 degrees Fahrenheit for 5 minutes.
Generously wash the outside of the butternut squash skin with hot water to remove bacteria that can transfer to the inside of the squash when you cut it.
Place the squash on a cutting board. Use a sharp knife to carefully slight the squash in half lengthwise.
Scoop out and discard the seeds.
Spray your air fryer basket with non-stick spray. Place the squash cut side up in the air fryer basket in a single layer.
Brush olive oil over the cut side of the squash halves, then sprinkle them generously with salt, pepper and chili powder (optional).
Air fry for 15 minutes, then place the butter on top of the squash in slices.
Air fry for an additional 10-15 minutes or until fork tender.
Serve immediately with fresh thyme and additional butter if desired.
Notes
For a sweet flavor, brush on 2 teaspoons of maple syrup for the last 2-3 minutes of cook time. Don't apply it earlier, the sugar burns pretty easily. You can also sprinkle on brown sugar.I used a 5.6 quart air fryer for this recipe.