Preheat oven to 400°F (200°C). Line 3 baking sheets with parchment paper.
In the bowl of a stand mixer fitted with the paddle attachment, beat butter and confectioners’ sugar, slowly increasing mixer speed to medium, until fluffy, 3 to 4 minutes, stopping to scrape sides of bowl. Add egg and vanilla, beating until combined.
In a medium bowl, whisk together flour, baking powder, and salt. With mixer on low speed, gradually add flour mixture to butter mixture, beating until a dough forms. Scrape sides of bowl, and knead dough 3 to 4 times in bowl to make sure everything is well combined.
Divide dough in half; cover one half with plastic wrap. On a heavily floured surface, roll remaining half to ¼-inch thickness. (Lightly flour top of dough if it sticks to rolling pin.) Using desired holiday cutters, cut dough, rerolling scraps as necessary. Using a small of set spatula, place cookies at least 1 inch apart on prepared pans.
Bake, one batch at a time, until lightly browned, 7 to 8 minutes. Let cool on pan for 5 minutes. Using a large of set or flat metal spatula, remove from pan, and let cool completely on wire racks. Decorate cooled cookies as desired with Royal Icing.
Recipe by Bake from Scratch at https://bakefromscratch.com/christmas-sugar-cookies/