Set each potato between chopsticks. Slice crosswise 1/8 inch apart without cutting through the base.

Preheat air fryer to 350°F. Rub potatoes with oil, salt and pepper; place cut-side up in the basket.

Air fry 25 minutes. Brush butter over the tops and into the cuts.

Raise heat to 400°F. Cook 15–20 minutes until golden and easily pierced; add 5 minutes if needed. Rest 3 minutes.