Preheat oven to 350°F (175°C) and lightly grease a donut pan.
In a bowl, whisk together flour, baking powder, sugar, and salt.
In another bowl, combine eggs, milk, melted butter, lemon juice, and zest until smooth.
Pour wet ingredients into dry ingredients and mix until just combined.
Fill donut pan cavities about three-quarters full with batter.
Bake for 10-12 minutes until golden brown; check doneness with a toothpick.
Cool slightly before removing from the pan. Optionally glaze or dust with powdered sugar.