Whisk together flour and salt in a medium-sized bowl.
Whip butter in an electric mixer on medium speed, gradually add in sugar and beat until light and fluffy, about 3-4 minutes.
Beat in lemon zest and vanilla. Add egg yolks and just mix until blended.
Turn mixer to low and gradually blend in flour mixture.
Divide dough in two halves, roll each into a 10” long log about 1 3/4? in diameter.
Wrap securely with plastic wrap. Logs can be shaped again once wrapped and starting to chill to ensure they keep their round log shape. Chill until firm, about 1 hour but this can be done up to 2 days in advance, but keep chilled.
Preheat oven to 350°F.
Line baking sheets with parchment paper or silpat liners. Remove the plastic wrap and, using a sharp knife, slice each log into 1/4” thick rounds. Place on cookie sheets about 1” apart.
Bake until cookies are firm but only slightly browned on the edges, about 14-16 minutes. Transfer to wire racks after cooling for 1 minute or so. Allow to cool completely. Repeat with remaining dough log, using cooled sheets and fresh parchment paper each time.
Icing Directions
Whisk together icing sugar and fresh lemon juice until smooth, adding more lemon juice if too thick to drizzle. Drizzle over cookies as desired. Immediately sprinkle decorative sprinkles if using. Allow icing to set for about 10 minutes before storing in airtight container.
By Epicurious
Recipe by Just a Smidgen at https://justasmidgen.com/2011/12/22/this-was-reality-she-thought-this-sense-of-clear-outlines-of-purpose-of-lightness-of-hope-ayn-rand-atlas-shrugged/