In a large mixing bowl, cream together the butter and confectioners’ sugar on medium-high speed until smooth, 1-2 minutes. Beat in the egg, vanilla extract, seeds scraped from the vanilla bean, and lemon zest until blended. Mix in the flour and salt on low speed just until incorporated. Form the dough into a ball and wrap tightly with plastic wrap. Refrigerate until chilled and firm, at least 1-2 hours.
When you are ready to bake the cookies, preheat the oven to 375˚ F. Line baking sheets with parchment paper. Roll the dough out on a well floured work surface to about ¼-inch thickness. Cut with cookie cutters as desired and transfer to the prepared baking sheets. Bake 8-10 minutes, rotating the sheets halfway through baking, until fully cooked but not at all browned. Allow to cool on the baking sheet 5 minutes, then transfer to a wire rack to cool completely. Decorate as desired.