01 - Preheat oven to 350°F. Lightly grease donut pan with oil or nonstick spray.
02 - Whisk together flour, baking powder, baking soda, salt, and cinnamon in a medium bowl until well blended.
03 - Beat sugar, eggs, Greek yogurt, oil, and vanilla extract in a large bowl until smooth and fully combined.
04 - Gradually add dry ingredients to wet mixture, folding gently until just combined. Avoid overmixing to maintain tender texture.
05 - Transfer batter to piping bag or zip-top bag with corner snipped. Pipe evenly into prepared donut pan cavities, filling each about 2/3 full.
06 - Bake for 10-12 minutes until lightly golden and toothpick inserted in center comes out clean.
07 - Let donuts rest in pan for 5 minutes, then carefully transfer to wire rack to cool completely.
08 - Whisk powdered sugar, milk, and vanilla until smooth. Dip cooled donuts in glaze and place on rack to set.