01 - In a large bowl, cream together the softened butter and 1/2 cup powdered sugar until light and fluffy using an electric mixer.
02 - Mix in the lemon juice, lemon zest, and vanilla extract until thoroughly incorporated into the butter mixture.
03 - Add the salt, flour, and cornstarch, mixing on low speed until a soft, uniform dough forms.
04 - Divide the dough in half and roll each half into a 1-inch diameter log. Wrap tightly in plastic wrap and refrigerate for at least 30 minutes until firm.
05 - Preheat oven to 350°F. 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 promptly to prevent overbrowning.
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 to cool completely. Dust with additional powdered sugar before serving for extra presentation.