01 - Preheat oven to 350°F (175°C) and line a baking sheet with parchment paper.
02 - In a large mixing bowl, beat the unsalted butter and powdered sugar together until the mixture is light and fluffy.
03 - Blend the lemon juice, lemon zest, and vanilla extract into the creamed butter mixture until homogeneous.
04 - In a separate bowl, whisk together all-purpose flour, cornstarch, and salt. Gradually add dry ingredients to the creamed mixture, mixing until a soft dough forms.
05 - Roll tablespoon-sized pieces of dough into balls and arrange evenly spaced on the lined baking sheet. Gently flatten each ball with your fingertips.
06 - Bake on the center rack for 10–12 minutes, until the cookies are set but remain pale. Remove from the oven and let stand on the baking sheet for 5 minutes before transferring to a wire rack to cool completely.
07 - Whisk powdered sugar and lemon juice together in a small bowl until completely smooth. Stir in lemon zest if desired for additional flavor.
08 - Dip or drizzle cooled cookies with the lemon glaze. Allow the glaze to set for 15 minutes before serving.