Add softened butter, confectioner's sugar, and granulated sugar to a large bowl. Whisk until light and fluffy.There is also no over beating at this point! This is when you want to really go for it. Whisk until as light as possible. Airiness during this step is absolutely essential. When you think that you've whisked them enough, whisk a little bit longer!
Quickly mix in lemon zest and lemon juice.
Whisk in the salt, flour, and corn starch until barely incorporated.This is the exact opposite of the butter mixing process! When you add flour, over mixing will make thee cookies dense and texturally unpleasant. In order to keep the airiness, mix as little as possible to stop seeing white pockets of flour.
On a lightly floured surface, roll out the dough until 1/4 inch thick.It can help to do this on top of waxed or parchment paper as well. This can help keep it from sticking to the countertop or to use less flour.
Roll over once more with the embossed rolling pin to imprint the pattern.
Cut out with cookie cutters and place 2 inches apart on a baking sheet.Alternatively, you can simply cut out the cookies into squares or rectangles. Cookie cutters are not actually necessary here unless you want to get fancy with it!
Bake for 45-50 minutes, or until just barely golden brown.
Move cookies from the baking sheet and place on a cooling rack or in the refrigerator to set completely.
Tips, Tricks, & Notes
For more information on the Fundamentals of Baking Cookies, check out my article on the matter. For instance, I recommend making cookies by hand with a fork and adding slightly less flour than called for.