In a large mixing bowl, cream together 1 cup of softened unsalted butter with ¾ cup of powdered sugar until light and fluffy, about 2-3 minutes. Mix in lemon zest, lemon juice, and vanilla extract until combined.

In a separate bowl, whisk together 2 cups of all-purpose flour, ½ cup of cornstarch, and ¼ teaspoon of salt. Gradually combine this with wet ingredients until a soft dough forms.

Divide the dough into two equal portions, roll into logs, wrap in plastic wrap, and refrigerate for at least 1 hour.

Preheat oven to 350°F (175°C) and line baking sheets with parchment paper. Slice each log into ¼-inch thick rounds and arrange them on the sheets.

Bake for 10-12 minutes or until edges are golden. Toss warm cookies in powdered sugar immediately after baking.

Cool cookies on a wire rack and if desired, coat again with powdered sugar.