01 - Preheat oven to 350°F. Lightly grease a donut pan with oil or nonstick cooking spray.
02 - In a medium bowl, whisk together the flour, baking powder, baking soda, salt, and cinnamon until well blended.
03 - In a large bowl, beat the sugar, eggs, Greek yogurt, oil, and vanilla extract until smooth and fully combined.
04 - Gradually fold the dry ingredients into the wet mixture, stirring gently until just incorporated. Avoid overmixing to maintain tenderness.
05 - Transfer batter to a piping bag or zip-top bag with one corner cut off. Pipe batter evenly into donut cavities, filling each about two-thirds full.
06 - Bake for 10-12 minutes until donuts are lightly golden and a toothpick inserted into the center comes out clean.
07 - Let donuts rest in the pan for 5 minutes, then carefully remove and transfer to a wire rack to cool completely.
08 - Whisk together powdered sugar, milk, and vanilla until smooth. Dip cooled donuts into glaze and return to rack until set.