Wash and thoroughly dry the sweet potatoes. Pierce each sweet potato 6–8 times on all sides with a fork.
Drizzle the sweet potatoes with olive oil and rub to coat. Sprinkle evenly with sea salt.
Arrange the sweet potatoes in a single layer in the air fryer basket or on the rack, making sure they are not touching.
Air fry at 400°F for 40–45 minutes, or until a knife or fork can be easily inserted into the center. Larger sweet potatoes may need a few additional minutes.
Carefully remove the sweet potatoes from the air fryer and let them cool for 2–3 minutes.
Slice each sweet potato open. Divide the butter evenly among the potatoes and season with salt and pepper before serving.