Preheat oven to 350ºF. Place oven rack in the center of the oven. Line a baking sheet with parchment paper or silpat.
In the bowl of your electric mixer fitted with the paddle attachment, beat the butter and sugar until light and fluffy.
Add the the egg, lemon zest, and vanilla beans.
In a separate bowl, sift together the flour and salt.
Gradually add the flour mixture to the creamed mixture and beat just until incorporated.
Scrape down the sides of the bowl as needed.
Divide the dough in half and shape each half into a flattened circle. Wrap each disk in plastic wrap and place in the refrigerator until firm (at least two hours or overnight).
Remove from fridge and use a rolling pin to roll dough out to about ¼ inch thick - I use dough spacers like these to get even cookies.
Cut into desired shapes and place on the baking sheet, spacing about 2 inches apart. Place in freezer for about 3-5 minutes.
Remove from freezer and bake the cookies for about 10 minutes, or until the edges of the cookies are a very light brown.
Remove from oven and place on a wire rack to cool. Decorate as desired.