- In a large bowl, whisk together all of the ingredients except for the steaks. Season with salt and pepper. Set aside half of the sauce in a small bowl. Cover and refrigerate until ready to serve.
- Add the steaks to the bowl of remaining sauce and toss to coat well. Cover and let marinate for 8 hours in the refrigerator.
- Preheat the grill, setting the burners to high. Oil the grate.
- Place the onions at the centre of a large piece of foil. Drizzle with half of the oil and all of the vinegar. Season with salt and pepper. Tightly seal the foil to form a packet. Cover the zucchini in the remaining oil. Season with salt and pepper.
- Drain the meat and set aside on a plate. Discard the marinade.
- Place the packet of onions directly on the grill and cook for 15 minutes, turning it over halfway through. Meanwhile, grill the steaks for 5 minutes on each side for rare or until the desired doneness. Set aside on a plate and let rest for 5 minutes. Grill the zucchini for 3 minutes on each side. Grill the naan breads for 1 minute on each side.
- On a work surface, slice the steaks. Serve with the zucchini, onions and naan. Garnish with the cilantro and serve with the reserved yogurt sauce.
While we generally use 11% yogurt in desserts, we have found that it works really well in marinades, too. Its high fat content allows it to resist the heat of the grill and perfectly tenderizes red meat such as beef and lamb. In sauces, its creaminess is second to none.