In a large glass bowl, combine the lamb with the garlic and other marinade seasonings. Cover and refrigerate for 4 hours to overnight.
Prepare to smoke by preheating the smoker up to 250°F and adding wood chips. If you are using a gas grill, fill a smoker tube with soaked wood chips, and before turning the grill on remove one set of grids, and place the smoker tube onto the sear plates. Leave the cooking grids off, and turn the grill on, preheating to 250°F. It is best to have two tubes on hand when smoking so that if you need to change the chips, you don’t have to work with a hot smoker tube.
Once the chips start to smoke and the smoker/grill is up to temperature, add the lamb making sure there is about one inch of space around each piece.
Smoke for 1 to 4 hours, turning a couple of times, and checking on the wood chips, adding more as necessary. Lamb is done when it reaches an internal temperature of 145°F.
While the lamb is smoking, combine the greek yogurt, garlic, turmeric, cinnamon, salt and pepper. Set aside to come to room temperature.
Chop the onion and peppers and toss the vegetables with melted coconut oil. Using a cast iron skillet, griddle, or the wok topper, grill the peppers and onion until cooked through, then season to taste with salt and pepper. Set aside.
Once the lamb is done, rest it on a plate or sheet pan for 5 minutes. Pour the drippings and the lemon juice into the yogurt sauce and mix thoroughly.
You can toss the lamb in the yogurt sauce before spooning over naan or couscous, then serving with extra sauce and grilled peppers, or serve everything with the sauce on the side.