1 pound plain whole milk yogurt
1/4 cup good olive oil, plus more for brushing grill
1 teaspoon lemon zest
1/4 cup freshly squeezed lemon juice (2 lemons)
5 tablespoons fresh whole rosemary leaves
6 cloves garlic, minced or mashed into a paste
1 teaspoon kosher salt
1/2 teaspoon freshly ground black pepper
2 pounds top round lamb or venison
1 red onion
2 tablespoons vegetable oil, divided
 
Combine the yogurt, olive oil, lemon zest and juice, rosemary, garlic, salt, and pepper in a large, non-reactive bowl. Divide the marinade in half, placing half in a bowl to be refrigerated and used for serving later. Add the lamb to the remaining marinade, making sure it is covered with the marinade, cover with plastic wrap and refrigerate overnight or for up to 2 days.
 
Prepare a charcoal grill with hot coals. Spread the coals in one tight layer on the grill.
Cut the lamb in 1 1/2-inch cubes. You should have about 20 cubes.
 
Cut the red onion in 8 pieces and separate each piece into 3 or 4 sections. Loosely thread 3 or 4 pieces of lamb onto skewers alternately with sections of onion. Sprinkle both sides of the lamb cubes with salt and pepper. Place the skewers on the hot grill and cook for 10 to 15 minutes, turning 2 or 3 times, until the lamb is medium-rare. Serve with pita, roasted potatoes or grilled okra and tomatoes and the reserved yogurt sauce.
 
Note: Rosemary stems can be used as skewers in place of bamboo or metal skewers. Simply remove the leaves. You’ll need to pierce the meat and onions with a metal skewer prior to threading the rosemary skewers through.