01 - In a large bowl, cream together softened butter and powdered sugar until light and fluffy using an electric mixer.
02 - Mix in fresh lemon juice, lemon zest, and vanilla extract until fully incorporated into the butter mixture.
03 - Add salt, flour, and cornstarch to the wet mixture, mixing until a soft, uniform dough forms.
04 - Divide dough in half and roll each half into 1-inch diameter logs. Wrap tightly in plastic wrap and refrigerate for at least 30 minutes until firm.
05 - Preheat oven to 350°F and line two baking sheets with parchment paper.
06 - Unwrap chilled dough and slice into 1/4-inch rounds. Arrange cookies on prepared baking sheets, leaving 1 inch of space between each.
07 - Bake for 10-12 minutes until edges are just barely golden. Remove from oven promptly.
08 - Let cookies cool on baking sheets for 5 minutes. While still warm, gently toss in powdered sugar to coat evenly.
09 - Transfer cookies to a wire rack and cool completely. Dust with additional powdered sugar before serving for extra zest.