In a small bowl, combine the lukewarm milk, 1 teaspoon of sugar, and the yeast. Let it sit for about 5-10 minutes until it becomes frothy.
In a large mixing bowl, whisk together the activated yeast mixture, egg, and melted butter until well combined.
In a separate bowl, mix together the 3 cups of all-purpose flour and 1/2 teaspoon of salt. Gradually add this to the wet mixture, stirring until a dough forms.
Transfer the dough to a floured surface and knead for about 5-7 minutes until smooth and elastic.
Place the dough in a greased bowl, cover it with a clean towel, and let it rise in a warm area for about 1 hour, or until it has doubled in size.
Once the dough has risen, punch it down and roll it out to about 1/2 inch thick. Use a donut cutter to cut out donuts and holes.
Preheat your air fryer to 350°F (175°C) for about 5 minutes.
Spray the air fryer basket with oil spray. Place the donuts in the basket, leaving space between them. Air fry for 5-7 minutes or until golden brown.
In a medium bowl, melt the 8 tablespoons of butter. Add the powdered sugar, vanilla extract, and enough warm milk to achieve a smooth, pourable consistency.
Once the donuts are done, let them cool slightly before dipping them into the glaze. Allow the excess glaze to drip off.
