Cut squash in half from stem to the bottom. Scrape seeds and soft membranes and discard.
Place flesh side up and add 1 Tablespoon butter to each cavity. Sprinkle with ½ Tablespoon brown sugar, salt and pepper to taste, and cayenne pepper if using (or season once squash is cooked).
Line air fryer with parchment paper (if desired). Add squash halves, flesh side up, to air fryer basket, and cook for 25 minutes or until the squash is fork tender.
Notes
Serve half squash for each person.
Refrigerate leftover air-fried acorn squash in a covered container for up to 4 days.
Freeze squash in zippered bags for up to 6 months.