In a medium bowl, mix the flour and salt until well combined. Set aside.
Using a hand mixer or stand mixer fitted with a paddle attachment, cream together butter, confectioners sugar, lemon zest, and vanilla extract until incorporated.
Scrape the bowl down and sift in the dry ingredients. Mix with a spatula until the dough starts to come together. It will look crumbly at first, but the dough will come together as you continue mixing.
Wrap the dough with plastic wrap. Chill the dough for at least 30 minutes in the refrigerator or until it is firm enough to cut through.
Preheat oven to 355°F/180°C and line two baking pans with parchment papers.
Take out the dough from the refrigerator and open the plastic wrap. Roll the dough into a 1/4-inch/5 mm thick slab. Cut the dough with a crinkle cutter or a sharp knife into 1.5-inch/4 cm rectangles. Place the cut dough on baking sheets, spaced at least an inch apart. Re-roll the scraps and refrigerate a few minutes until firm again and repeat the process until all dough is used.
Use a skewer to poke holes in the cookies (optional).
Chill in the refrigerator for another 30 minutes if the dough has warmed up.
Bake for 13-16 minutes or until the bottom edges of the cookies are golden brown in color.
Transfer to a wire sheet to cool completely.
Notes
Use cake flour for light, crisp, and tender cookies. Use all-purpose flour for softer and chewier cookies.