Combine dry ingredients: In the medium mixing bowl mic flour, cornstarch, salt and baking soda. Set aside.
In a large bowl using a hand mixer or stand mixer cream butter and granulated sugar until light and fluffy.
Beat in egg, add lemon juice, lemon zest and vanilla extract. Mix until well combined.
Gradually add flour mix. Dough should become thick, sticky but creamy
Cover the bowl with plastic wrap and refrigerate for 2 hours.
Remove cookie dough from the refrigerator.
Preheat the oven for 350 F. Line the baking sheet with parchment paper.
Take tablespoon-sized portions of dough and roll them into balls.
Roll each ball in the confectioner’s sugar. Place them on a baking sheet 3 inches apart.
Flatten the cookies by gently pressing down on each dough ball with the bottom of a glass or your fingers.
Bake for 11- 13 minutes until the edges of the cookies are lightly golden.
Cool them for about 5 minutes on the baking sheet then transfer them to a cooling rack.