Wash and thoroughly dry 6 medium sweet potatoes. Use a fork to poke each sweet potato 6-8 times on all sides.
Drizzle 1 tablespoon olive oil evenly over the sweet potatoes and rub to coat. Sprinkle 2 teaspoons sea salt evenly over all of the potatoes.
Arrange the sweet potatoes in a single layer in the air fryer basket or on the air fryer rack, making sure they are not touching so the air can circulate around them.
Air fry at 400 degrees F for 40-45 minutes, or until a knife or fork can be easily inserted into the center of each sweet potato. Larger potatoes may require a few additional minutes of cooking.
Carefully remove the sweet potatoes from the air fryer and allow them to cool for 2-3 minutes.
Slice each sweet potato open and top with 3 tablespoons butter, dividing it evenly among the 6 potatoes.
Season with 1 teaspoon salt and 1 teaspoon black pepper, dividing evenly before serving.