In a mixing bowl, combine flour, baking powder, and salt.
Add diced butter to flour mixture, and with your hands, massage the butter into the flour.
Using a dough hook, knead the dough on medium speed, slowly adding the buttermilk until a dough ball forms.
Lightly dust a flat surface with flour, and flatten dough to 1 1/2 inches thick.
Using a wide mouth mason jar, or something of a similar size, punch out the biscuits. Re-knead and flatten excess dough for more biscuits.
Place biscuits in the air fryer basket, brush tops with melted butter, and cook at 370 for five minutes on each side.
Notes
Note that the butter must be chilled. If the biscuit dough starts to feel extra sticky and becomes hard to work with, put it in the refrigerator until it's cold. You can also make these in your Ninja Foodi.