Make filling by melting butter and adding brown sugar and cinnamon. Stir to combine.
Sprinkle a cutting board/surface generously with flour. Place dough on board and flatten into a small rectangle with fork. Pour filling on top and spread with a spatula.
Cover hands with flour and roll dough into a log (rolling along the longer rectangle side). Cut into even pieces. 8 pieces. I cut the log in half first then cut each half into 4.
Lightly spray muffin cups (cupcake liners) with cooking spray. Once pieces are cut, place into cupcake lines (I suggest using sturdy ones).
Set air fryer for 325, 15 minutes
Depending on the size of your air fryer, you should be able to fit 4 in the basket. Be sure to leave a little space on the sides. I like to peek in the basket around 12 minutes to make sure they're not cooking/browning too fast. Make frosting while muffins are cooking.
When timer on the air fryer rings, pull them out. The muffins are done with a toothpick comes out clean in the center. Take the muffins out of the basket carefully (they're hot), put on plate or cooling rack.
Let cool a bit (maybe 5 min.) before frosting is put on. If you want it more melted in drizzle, frost when warm.