Whisk the flour, cornstarch, baking soda, and salt together in a medium bowl. Set aside.

Place the butter and sugar in a small food processor and cream until the butter and sugar are smooth, then add the egg yolk, lemon juice, zest, and vanilla and continue to mix in the food processor until blended. It’s okay if it looks a little curdled, that from the lemon juice. .

Transfer to a medium bowl and mix in the flour using a spatula. The dough will be a little sticky and thick.

Cover dough tightly with plastic wrap and chill for at least 2 hours, however you can let it chill overnight.

Preheat oven to 350°F Line baking sheets with parchment paper or silicone baking mats. Set aside.

Remove cookie dough from the refrigerator.

Use a 1 tablespoon cookie scoop to evenly divide the dough into 5 cookie balls.

Roll the balls in the granulated sugar , then roll each ball very generously in the powdered sugar.

Place 3 inches apart on the baking sheet. Bake the cookies for 13–15 minutes or until the edges appear set and the centers still looks a bit sof