Buttery Sugar Cookies

In a large bowl, using an electric mixer on medium-high speed, beat the butter and sugar, stopping occasionally to scrape down the bowl, until fluffy and pale yellow, about 2 minutes. Beat in the egg and vanilla, stopping once or twice to scrape down the bowl, about 1 minute more. Add the flour and salt. Mix on low until just blended. Divide the dough into two disks and wrap in plastic. Refrigerate the dough until firm, 2 to 3 hours.

Arrange the racks in the top and bottom thirds of the oven; preheat to 350°. Roll out 1 disk of dough between 2 sheets of parchment paper to about 1/4 inch thick. Peel off the top sheet of parchment and, using cookie cutters, cut out the cookies. Divide between 2 parchment-lined baking sheets.

Bake the cookies, rotating and reversing the sheets halfway through, until pale golden, 10 to 12 minutes. Let cool on the sheets for about 5 minutes, then transfer to wire racks to cool completely. Repeat with the remaining dough on cooled, parchment-lined baking sheets.

Decorate the cookies with the Royal Icing. Let dry for at least 1 hour or overnight. Store in an airtight container, layering the cookies between sheets of parchment.