Make The Coffee Cake: In a small bowl, cream the butter and granulated white sugar, then fold in the vanilla extract and egg, and mix well. Then fold in the all-purpose flour, baking powder, salt, and milk, and mix well.
Make The Filling: In a small mixing bowl, mix together the butter, ground cinnamon, flour, and brown sugar, mix well.
Make The Topping: In a small bowl, mix together the butter, flour, brown sugar, and ground cinnamon.
Prepare the Pan: Use either a bundt cake pan or a small baking pan. The size of the pan will depend on the air fryer that are you are using. Grease the pan with cooking spray.
Fill The Cake Pan: Pour half of the cake batter into the prepared pan. Then sprinkle the filling over the cake batter, then cover the filling with the rest of the cake batter. Sprinkle the topping over the top.
Cook: Set the cake into the air fryer basket and cook for 15 to 30 minutes at 320 degrees F, using the air fryer setting. Air Fry until the toothpick when inserted into the middle of the cake, comes out clean.