Preheat the air fryer to 375° if required by your fryer model.
Whisk together the flour, baking powder, salt and sugar.
Cut the softened butter into the flour mixture with a pastry blender or fork.
Add the milk and stir until a soft dough forms.
Turn the dough out onto a floured surface and knead the dough until smooth and no longer sticky.
Separate the dough into eight equal balls. Roll each ball between your hands to form a long rope, then twist the ends together to form a knot.
Cook the pretzels in the air fryer for 15 minutes, until golden brown. Watch the cooking time for your pretzels. It may differ depending on the model of your air fryer.
After the pretzels are cooked, brush each one with melted butter and top with coarse salt.