Cook your pasta of choice until it's done. Drain. Allow to completely cool.
Dice your leftover smoked turkey. Dice a rib of celery.
Grate as much onion as you want to use and set aside.
In a mixing bowl, combine the cooled pasta with the mayonnaise, diced smoked turkey, diced celery, and grated raw onion. With a spatula fold in all the ingredients to combine.
Add in garlic powder and then salt to your personal taste.
Chill in the fridge for at least 1 hour before eating. But several hours will give the flavors longer to meld together.