In a large mixing bowl, combine the grated onion, minced garlic, plain yogurt, olive oil, lemon juice, ground cumin, ground coriander, ground paprika, ground black pepper, salt, and ground cinnamon. Mix well.
Add the lamb cubes to the marinade, ensuring each piece is well coated. Cover the bowl with plastic wrap and refrigerate for at least 2 hours, preferably overnight, to allow the flavors to meld.
If using wooden skewers, soak them in water for at least 30 minutes to prevent burning.
Thread the marinated lamb cubes onto the skewers, leaving a little space between each piece for even cooking.
Preheat your grill to medium-high heat. If using a charcoal grill, allow the coals to burn until they are covered with white ash.
Place the skewers on the preheated grill and cook for about 10-12 minutes, turning occasionally, until the lamb is cooked to your desired level of doneness and has a nice char on the outside.
Remove the kebabs from the grill and transfer to a serving platter. Garnish with freshly chopped parsley.
Enjoy your meal!