Measure flour and salt into a bowl. Set aside.
Cream butter and sugar together until light and fluffy.
Add vanilla, 1 teaspoon of lemon zest, and flour mixture (in 2 parts).
Drop cookie dough between two sheets of parchment and roll until ¼-inch thick.
Refrigerate for 30 minutes.
Preheat the oven to 350° and line a sheet tray with parchment.
Remove rolled out dough from the fridge, and cut cookies out with a 1 1/2 - 2-inch cutter with as little space between them as possible.
Arrange cookies on a parchment lined sheet, leaving at least 2 inches between cookies.
Use a butter knife to make 3-4 lines across the cookie, intersecting in the center to create a lemon-ish look.
Bake for 8-11 minutes, turning halfway through baking.
Remove from the oven when edges are just beginning to brown, and let cool for at least an hour.
Mix confectioners sugar, 1 tsp lemon zest, and lemon juice carefully, only adding as much liquid as is needed to create a thick glaze.
You can also add more lemon zest for an extra zesty cookie.
Holding onto the sides, dip the butter knife-hatched face of the cookie into the glaze, allow a few moments for the extra to drip off, and then let them harden glaze-side up.
Let harden for at least an hour before serving or storing.