In a stand mixer, blend melted butter, granulated sugar, vanilla extract, and lemon zest until well combined.
Add lemon juice and egg, mixing on low until everything comes together.
Slowly introduce flour, corn starch, baking soda, and salt while keeping the mixer on low. Mix until just combined.
Cover the bowl with plastic wrap and let the dough chill in the fridge for 30-60 minutes.
Once the dough is ready:
Preheat the oven to 350°F and line a cookie sheet with parchment paper.
Scoop out about 2 tablespoons of dough per cookie using a medium cookie scoop.
Roll each dough ball in the remaining granulated sugar.
Space the cookies 1-2 inches apart on the prepared sheet and bake for 9 minutes or until the edges are just set.
Allow the cookies to cool on the sheet for 5 minutes before transferring them to a cooling rack.