01 - Cream softened butter and powdered sugar in large bowl until light and fluffy using electric mixer.
02 - Blend in lemon juice, lemon zest, and vanilla extract until fully incorporated.
03 - Mix salt, flour, and cornstarch into butter mixture until soft dough forms.
04 - Divide dough in half, roll each into 1-inch diameter logs, wrap in plastic, and refrigerate 30 minutes.
05 - Heat oven to 350°F and line baking sheets with parchment paper.
06 - Unwrap chilled dough and cut into 1/4-inch rounds. Place 1 inch apart on prepared sheets.
07 - Bake 10-12 minutes until edges are barely golden.
08 - Let cool 5 minutes on sheets, then gently toss in powdered sugar while warm.
09 - Transfer cookies to wire rack to cool completely. Dust with extra powdered sugar before serving.