In a medium-size mixing bowl, mix together all your dry ingredients: oat flour, self-rising flour, granulated stevia, baking soda, baking powder, and salt.
In the same bowl, add in wet ingredients: egg, yogurt, unsweetened applesauce, skim milk, lemon zest, lemon juice, lemon extract, and mashed blueberries. Mix until all ingredients are well combined.
Transfer the batter to a piping bag and pipe evenly into donut silicone or tin molds. Makes 18 small-sized donuts.
Bake at 325 for about 20 minutes or until toothpick comes out clean. Let cool.
Create the glaze using the remaining confectioner's stevia and skim milk. Mix in a small bowl. Drizzle over donuts as desired.