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.