Soak the wood chips in water for at least 30 minutes.
In a large bowl gently combine the ground chuck, cumin, pepper and 1½ teaspoons of salt. Shape into four patties of equal size, each about 2 centimetres thick. With your thumb or the back of a spoon, make a shallow indentation about 2.5 centimetres wide in the centre of the patties to prevent them from forming a dome as they cook. Cover and refrigerate until ready to grill.
Prepare a two-zone fire for high heat (230°C to 290°C).
In a medium skillet over medium heat on the stove, warm 1 tablespoon of the oil. Add the onion and garlic and cook until the onion is tender, about 3 minutes, stirring occasionally. Transfer to a medium bowl. Brush the tomatoes with the remaining 1 tablespoon of oil.
Related Grill Skills
Chopping an Onion
Brush the cooking grate clean. Drain and add half of the wood chips to the charcoal and put the lid on the grill. When smoke appears, place the tomato halves, cut-side up, over indirect heat. Close the lid and cook until the tomato juices are bubbling and the skins split, about 12 minutes. Remove from the grill. Remove and discard the tomato skins and roughly chop the tomatoes. Add the tomatoes, cilantro, chile peppers and lime juice to the onion mixture. Season with salt. Set aside.
Drain and add the remaining wood chips to the charcoal and put the lid on the grill. When smoke appears, cook the patties over direct high heat, with the lid closed, until cooked to medium doneness (70ºC), 8 to 10 minutes, turning once. During the last minute of cooking time, place a slice of cheese on each patty to melt and toast the rolls, cut-side down. Remove from the grill. Build each burger on a bun with a patty and the salsa. Serve warm.