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 well combined and evenly distributed throughout the mixture.
03 - Add the salt, flour, and cornstarch, mixing on low speed until a soft dough forms. Be careful not to overmix.
04 - Divide the dough in half and roll each half into a log about 1 inch in diameter. Wrap 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 and set aside.
06 - Unwrap the chilled dough and slice into 1/4-inch rounds. Place cookies on prepared baking sheets, spacing them about 1 inch apart to allow for slight spreading.
07 - Bake for 10-12 minutes, or until the edges are just barely golden. The centers should remain pale and tender.
08 - Remove from oven and let cool on the baking sheets for 5 minutes. While still warm, gently toss cookies in powdered sugar to coat evenly.
09 - Transfer cookies to a wire cooling rack and let cool completely. For an extra zesty finish, dust with additional powdered sugar before serving.