In a large bowl, cream together the butter, sugars, and egg until smooth, about 5 minutes with electric mixer on medium-high setting.

Mix in the baking powder, baking soda, cinnamon, and oats to the creamed mixture. Mix thoroughly, making sure to scrape the sides.

On low speed, add the whole-wheat pastry flour and milk. Mix well. Add the Greek yogurt, applesauce, and all-purpose flour. Mix until combined, being careful not to overmix.

Fill the prepared donut pan or muffin tin and bake for 12–15 minutes. You can also roll them into balls and place on a baking sheet for donut holes.

Let cool in the pan for a few minutes, then place on wire rack for 5 minutes to cool before adding a glaze.

While donuts are cooling prepare the Vanilla Yogurt Glaze by mixing both ingredients in a small bowl until smooth and pour on top cooled donuts.