Cream the Butter and Sugar: In a large mixing bowl, beat the softened butter and powdered sugar together using an electric mixer until light and fluffy (about 2–3 minutes).
Add the Lemon and Vanilla: Mix in the lemon zest, lemon juice, and vanilla extract, ensuring everything is evenly combined.
Combine Dry Ingredients: In a separate bowl, whisk together the all-purpose flour, cornstarch, and salt.
Mix Wet and Dry Ingredients: Gradually add the dry ingredients to the butter mixture, mixing just until the dough comes together. Do not overmix.
Chill the Dough: Wrap the dough in plastic wrap or shape it into a log and wrap. Refrigerate for at least 1 hour to firm up. This step is crucial for shaping and baking.
Shaping and Baking
Preheat the Oven: Preheat your oven to 350°F (175°C). Line baking sheets with parchment paper.
Shape the Cookies: Roll the chilled dough into small balls (about 1 inch in diameter) or slice the log into discs. Place the cookies on the prepared baking sheets, spacing them about 1 inch apart.
Bake: Bake for 12–14 minutes or until the edges are just starting to turn golden. The cookies should remain pale.
Coating
Cool Slightly: Allow the cookies to cool on the baking sheet for 5 minutes before transferring to a wire rack.
Dust with Powdered Sugar: While the cookies are still warm, gently roll them in powdered sugar or use a sieve to dust them generously. Let the cookies cool completely, then give them a second coating of powdered sugar for an extra touch of sweetness.