In a large bowl, combine the ground lamb, grated onion, minced garlic, parsley, cumin, coriander, paprika, cinnamon, salt, and black pepper. Squeeze the grated onion to remove excess liquid before adding it. Mix with your hands until the spices are evenly distributed, but do not overwork the meat.
Divide the mixture into 8 equal portions. Shape each one into an oval log about 4 inches long and 1 inch thick. If using wooden skewers, soak them for 20 minutes first, then mold the meat around the skewers. Alternatively, shape them as free-form logs without skewers.
Preheat the air fryer to 400 degrees F for 3 minutes.
Spray the air fryer basket lightly with olive oil spray. Arrange the kebabs in a single layer with space between each one. Spray the tops lightly with olive oil spray.
Air fry at 400 degrees F for 10 to 12 minutes, turning the kebabs once halfway through, until they are nicely browned on the outside and cooked through with no pink remaining in the center.
While the kebabs cook, prepare the yogurt sauce. Stir together the greek yogurt, lemon juice, chopped mint, grated garlic, and a pinch of salt in a small bowl.
Serve the lamb kebabs hot with the yogurt sauce drizzled over the top or on the side. They pair beautifully with warm pita bread and a simple cucumber-tomato salad.