In a medium bowl, beat the softened butter, lemon zest, sugar, salt, and vanilla with an electric mixer until light and fluffy.
In a separate bowl, whisk together the flour, cornstarch, and baking powder until well combined.
Fold the dry ingredients into the butter mixture using a spatula. Mix just until no flour streaks remain—do not overmix.
Cover the bowl tightly and refrigerate for at least 1 hour. This prevents the cookies from spreading too much in the oven.
Use a small cookie scoop to portion 1 tablespoon of dough. Roll into smooth balls and place them on a parchment-lined baking sheet.
Gently press down on each ball with your palm to slightly flatten. Bake at 180°C (350°F) for 9–11 minutes until set but still pale.
Let the cookies cool slightly until warm to the touch. Roll them generously in a bowl of powdered sugar until fully coated, then serve!
Notes
Use Room Temperature Butter: Your butter should be soft enough to leave an indent when pressed, but not oily. This ensures it creams perfectly with the sugar for a light cookie.
Don't Skip the Cornstarch: This is the "secret" to the cooler texture. It breaks up the gluten in the flour to create a delicate, sandy crumb that dissolves on your tongue.
The Double-Coat Method: For a thick, snowy look, roll the cookies in powdered sugar while they are warm (not hot) so the first layer sticks. Once they are completely cool, roll them a second time for a professional finish.
Measure Flour Correctly: Avoid scooping flour directly with your measuring cup, which packs it down. Instead, spoon the flour into the cup and level it off with a knife to keep the cookies from becoming dry or cakey.
Fresh is Best: Always use freshly squeezed lemon juice and zest. Bottled juice can have a bitter aftertaste that overpowers the delicate butter flavor of these cookies.
Watch the Oven Closely: These cookies should stay pale and light. Do not wait for the edges to turn golden brown, or they will lose their signature soft texture.