ULTIMATE SUGAR COOKIES

Steps:

• Place racks in lower and upper thirds of oven; preheat to 325°F. Whisk salt, baking powder, and 3 cups flour in a small bowl. Using an electric mixer on high speed, beat butter and sugar until well combined (butter does not need to be fluffy), about 3 minutes. Add egg, egg yolk, and vanilla; beat just to combine. Reduce speed to low and gradually add dry ingredients; mix just to combine. Form dough into two 3/4"-thick disks; wrap in plastic. Chill at least 2 hours.
• Let 1 disk of dough sit at room temperature until softened slightly, about 5 minutes. Roll out on a lightly floured sheet of parchment paper until about 1/4" thick, dusting with flour as needed (if dough gets soft or sticky, chill on parchment until firm). Cut out shapes with floured cookie cutters; transfer to parchment-lined baking sheets.
• Bake cookies, rotating baking sheets halfway through, until edges are golden, 12-16 minutes, depending on size. Transfer to wire racks and let cool. Repeat with scraps and remaining dough.
• Decorate cooled cookies as desired.
• MAKE AHEAD: Cookie dough can be made 1 month ahead; freeze instead of chilling. Cookies can be baked (left undecorated) 2 weeks ahead; wrap tightly and freeze.