Preheat oven or roaster oven to 400 degrees Farenheit.
Place onion, water, and bay leaves in the bottom of the roaster pan.
In a small bowl, add salt, sugar, paprika, celery salt, cornstarch, onion and garlic powder, and cayenne pepper and mix well with a fork.
Place pork butt onto the rack inside the roasting pan. Pour 2 ounces of liquid smoke over one side of the roast. Massage 1/2 of the dry mixture into the roast. Repeat the process on the other side of the roast. Place in the oven until thermometer reads 170 degrees Farenheit (usually 2 hours).
Remove from oven onto a cutting board and allow to cool for about 5 minutes. Either slice or pull apart with two forks, mixing a little of the pan juices into the pulled pork.
Serve on hamburger buns or Hawaiian rolls with coleslaw.