01 - Preheat oven to 350°F. Lightly grease a donut pan with oil or nonstick cooking spray.
02 - In a medium bowl, whisk together flour, baking powder, baking soda, salt, and cinnamon until well blended.
03 - In a large bowl, beat sugar, eggs, Greek yogurt, oil, and vanilla extract until smooth and fully combined.
04 - Gradually add dry ingredients to wet ingredients, mixing gently until just incorporated. Avoid overmixing to prevent tough donuts.
05 - Transfer batter to a piping bag or zip-top bag with corner snipped. Pipe batter evenly into prepared donut cavities, filling each about 2/3 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 pan for 5 minutes, then carefully turn out onto a wire rack to cool completely before glazing.
08 - Whisk together powdered sugar, milk, and vanilla until smooth. Dip tops of cooled donuts into glaze and place on rack to set.