Mix together ½ cup white sugar and butter together in a medium bowl until it becomes crumbly. Add the 2 large egg yolks and stir until combined.

Add flour, baking powder and salt into a separate bowl. Add ⅓ of the flour mixture, ¼ cup of brown sugar and ½ the sour cream into the sugar-egg mix and stir until these are combined together. Mix in the remaining flour and sour cream; then refrigerate dough until ready for use.

Mix 1 tsp pumpkin spice, 2 ½ tsp white sugar, and 1 ½ tsp cinnamon together in a bowl. Preheat air fryer to 350°.

Roll the dough out on a lightly floured surface to about ¾" thick. Using a 3- inch and a 1- inch cookie cutter, cut 6 large circles in the dough and then cut holes in the middle of each to form the doughnut shapes. Or, if you have a donut cutter, you will be able to cut the donut and hole at the same time.

Brush half of the melted butter over each side of the doughnuts.

Place half of the doughnuts into the air fryer basket in a single layer and cook for 8 minutes. Remove the doughnuts from the fryer and brush cooked donuts with remaining melted butter and immediately dip into the cinnamon/pumpkin spice/sugar mix.

Repeat these steps with the remaining doughnuts. You may need to adjust cooking times according to your particular air fryer. Enjoy while warm!