Mix the powdered sugar and flour in a bowl. Add the salt, egg yolk, and apricot liqueur. Add the grated orange peel and butter, then work everything together until you have a smooth dough.
Preheat the oven to 180°C / 356°F. Transfer the dough to a piping bag fitted with a large star nozzle. Pipe stars about 4 cm in size onto a baking sheet lined with baking foil. Bake on the middle rack for 12-15 minutes. Cool on a wire rack.