01 - Preheat the oven to 350°F and lightly grease a standard donut pan.
02 - In a large bowl, whisk together mochiko, sugar, baking powder, and salt until well blended.
03 - In a separate bowl, beat eggs, then whisk in milk, melted butter, lemon juice, lemon zest, and vanilla extract until smooth.
04 - Pour the wet ingredients into the dry ingredients. Stir until just combined and smooth, being careful not to overmix.
05 - Transfer batter to a piping bag or zip-top bag. Pipe evenly into the prepared donut pan, filling each cavity about 3/4 full.
06 - Bake for 18-20 minutes, or until donuts are puffed and lightly golden. A toothpick inserted into the center should come out clean.
07 - Let donuts cool in the pan for 5 minutes, then carefully transfer to a 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 lemon juice if needed.
09 - Dip the tops of cooled donuts into the glaze, allowing excess to drip off. Place on a wire rack and let the glaze set for about 15 minutes before serving.