- Prepare a square baking pan with parchment paper and set aside. 
- Brown the butter for both the blondies and the icing together. Place the butter slices into a skillet over medium heat and melt while stirring constantly. Continue to cook for 5-7 minutes or until small brown flecks begin to form. Remove from heat and pour into a glass bowl or container until ready for use. 
- Add the diced apples, ⅓ cup of brown sugar, and ½ teaspoon of ground cinnamon to the pan used for the butter. Cook for 4-5 minutes over medium heat until softened; remove from heat and set aside 
- In a large mixing bowl, combine the flour, baking powder, salt,  and remaining cinnamon. 
- In a separate mixing bowl, combine a cup of the browned butter, remaining brown sugar, eggs, and vanilla extract until well mixed. 
- Stir the browned butter mixture into the flour mix and stir until just combined. Fold the apples into the mixture. 
- Spread half of the mixture into the bottom of the prepared baking pan. (This recipe makes two batches) 
- Set the air fryer setting to 320 degrees and bake for 12-15 minutes or until the blondies are cooked through.  
- While the blondies cool, make the icing. Stir together the remaining browned melted butter, confectioners sugar, milk and ½ teaspoon vanilla extract until well mixed and smooth. Drizzle or spread over the blondies. 
- Slice into bars and serve. Great topped with a scoop of ice cream, enjoy!