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

In a large mixing bowl, cream together softened unsalted butter and powdered sugar until light and fluffy, about 2-3 minutes.

In a separate bowl, whisk together cornstarch, all-purpose flour, lemon zest, and salt. Gradually add the dry mixture to the creamed butter and sugar, then mix in fresh lemon juice and vanilla extract until a soft dough forms.

Roll the dough into 1-inch balls and place them on the lined baking sheet, flattening each one slightly.

Bake for 10-12 minutes until the edges are light golden and the centers remain soft.

Allow the cookies to cool on the baking sheet for 5 minutes before transferring to a wire rack. Dust with additional powdered sugar before serving.