01 - Preheat oven to 350°F and lightly grease a standard donut pan with cooking spray or butter.
02 - In a large bowl, whisk together sweet rice flour, granulated sugar, baking powder, and sea salt until evenly distributed.
03 - In a separate bowl, beat eggs until frothy. Whisk in milk, melted butter, lemon juice, lemon zest, and vanilla extract until smooth.
04 - Pour wet mixture into dry ingredients. Stir gently until just combined and smooth, being careful not to overmix.
05 - Transfer batter to a piping bag or zip-top bag with corner snipped. Pipe batter into prepared donut pan cavities, filling each about 3/4 full.
06 - Bake for 18-20 minutes until donuts are puffed and lightly golden. A toothpick inserted into the center should come out clean.
07 - Let donuts rest in pan for 5 minutes, then carefully transfer to wire rack to cool completely before glazing.
08 - Whisk together powdered sugar, lemon juice, and lemon zest until smooth and pourable. Adjust consistency with additional juice if needed.
09 - Dip tops of cooled donuts into glaze, allowing excess to drip off. Return to wire rack and let glaze set for 15-20 minutes before serving.