01 - Beat softened butter and powdered sugar in large bowl until light and fluffy, approximately 2-3 minutes.
02 - Mix in fresh lemon juice, lemon zest, and vanilla extract until thoroughly incorporated.
03 - Add salt, flour, and cornstarch, mixing just until soft dough forms and no dry streaks remain.
04 - Divide dough in half and roll each into 1-inch diameter logs. Wrap in plastic and refrigerate 30 minutes until firm.
05 - Preheat oven to 350°F. Line baking sheets with parchment paper.
06 - Unwrap dough and slice into 1/4-inch rounds. Arrange on prepared sheets with 1-inch spacing.
07 - Bake 10-12 minutes until edges are barely golden.
08 - Cool 5 minutes on baking sheets, then gently toss warm cookies in powdered sugar until evenly coated.
09 - Transfer to wire rack and cool completely. Dust with additional powdered sugar before serving.