Preheat the oven to 350°F and line two sheet pans with parchment
Add the butter to the mixer and beat with the paddle attachment until smooth and shiny
Add the sugar, orange zest, salt and vanilla and mix on medium speed until shiny and spreadable like frosting, about 2-3 minutes
Whip in the egg until emulsified
Add the flour and mix just until combined
Transfer the dough to a piping bag fitted with a large open star tip
Pipe onto the parchment lined tray, leaving about 1 inch space in between each cookie
Top with sprinkles
Bake one tray at a time in the middle rack for 12-15 minutes, rotating halfway, until barely golden and fragrant
Repeat with the second tray and cool the cookies in the pan
If dough is too firm to pipe, microwave at full power in 10 second increments, stirring after each, until smooth enough to spread
