Preheat your oven to 350°F (175°C) and line a baking sheet with parchment paper.

In a large bowl, beat the softened butter and powdered sugar together until light and fluffy.

Add the vanilla extract, lemon zest, and lemon juice to the butter mixture, and mix until well combined.

In a separate bowl, whisk together the all-purpose flour, cornstarch, and salt. Gradually add the dry ingredients to the wet ingredients, mixing until a soft dough forms.

Scoop out small portions of dough (about 1 tablespoon each) and roll them into balls. Place them on the prepared baking sheet, spacing them about 2 inches apart.

Gently press down on each dough ball with your fingers or the bottom of a glass to slightly flatten the cookies.

Bake for 10–12 minutes, or until the edges are set but not browned. Remove from the oven and allow to cool on the baking sheet for a few minutes before transferring to a wire rack to cool completely.

For the glaze (optional), whisk together the powdered sugar, fresh lemon juice, and lemon zest until smooth. Drizzle or spread the glaze over the cooled cookies.