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 combined.
03 - In another bowl, beat eggs, then whisk in milk, melted butter, lemon juice, lemon zest, and vanilla until smooth.
04 - Pour the wet ingredients into the dry ingredients. Stir until just combined and smooth, being careful not to overmix.
05 - Spoon the batter into 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 should come out clean.
07 - Let donuts cool in the pan for 5 minutes, then transfer to a wire rack to cool completely.
08 - Whisk together powdered sugar, lemon juice, and zest until smooth and pourable.
09 - Dip cooled donuts into the glaze, allowing excess to drip off. Place on a rack to set before serving.