In a medium bowl combine ground beef, salt, cumin, and chili powder. Mix with hands to combine. Form into four 1/3 lb patties.
When ready to cook, start the Traeger grill on Smoke with the lid open until the fire is established (4 to 5 minutes). Set the temperature to 350 degrees F and preheat, lid closed, for 10 minutes.
Toss the garlic with 1-1/2 teaspoons oil and a pinch of salt and black pepper; seal them in foil to form a pouch. Brush the onions with the remaining 1-1/2 teaspoons oil and sprinkle with salt and black pepper to taste.
Grill the whole chiles, onions and garlic for about 15 minutes, until the chiles are blackened all over (turning them every 5 minutes), and the onions are tender and grill-marked (turning them, and the garlic pouch, after 7 or 8 minutes).
Place the chiles in a bowl, cover with a plate or plastic wrap, and steam the skins loose, about 10 minutes. Peel and seed the chiles, chop finely and transfer to a medium bowl.
Meanwhile, finely chop the garlic and the onions and add to the chiles. Add 1/2 teaspoon salt, stir to mix, and set aside until ready to use.
Place the burger patties on the grill and cook each side 4 minutes or until desired doneness (140 degrees F for medium). In the last minute or two, top each patty with cheese to melt.
Lightly toast the burger buns if desired.
To build the burger, place patties on burger buns, top each patty with a little of the green chile mixture, lettuce and tomato or desired toppings. Enjoy!
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