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 together the sugar, eggs, Greek yogurt, vegetable oil, and vanilla extract until the mixture is smooth and fully combined.
04 - Gradually add the dry ingredients to the wet ingredients, mixing gently with a spatula until just combined. Avoid overmixing to ensure tender donuts.
05 - Transfer the batter to a piping bag or a zip-top bag with one corner snipped off. Pipe the batter evenly into the prepared donut pan, filling each cavity approximately 2/3 full.
06 - Bake for 10-12 minutes, or until the donuts are lightly golden and a toothpick inserted into the center comes out clean.
07 - Let the donuts cool in the pan for 5 minutes, then carefully remove them and transfer to a wire rack to cool completely.
08 - In a small bowl, whisk together the powdered sugar, milk, and vanilla extract until smooth and creamy. Dip the tops of the cooled donuts into the glaze and place them back on the wire rack to set.