Preheat your smoker to 225°F.

Season the chuck roast evenly with kosher salt, black pepper, and garlic powder.

Place the chuck roast directly on the smoker's grate and cook for about 3-4 hours, or until the internal temperature reaches 160°F.

In a disposable aluminum pan, combine the sliced onion and 2 cups of beef broth. Place the roast in the pan and cover tightly with aluminum foil.

Continue smoking for an additional 3-4 hours until the internal temperature of the roast reaches 205°F.

Remove the roast from the smoker and let it rest for 15 minutes before slicing. Serve with the onions and broth from the pan.