01 - In a large bowl, combine olive oil, Greek yogurt, lemon juice, minced garlic, cumin, coriander, smoked paprika, black pepper, salt, cinnamon, and optional chili flakes. Stir until well blended.
02 - Add lamb cubes to the marinade and toss to ensure even coating. Cover and refrigerate for at least 1 hour; for optimal flavor and tenderness, marinate overnight.
03 - Preheat a grill or grill pan over medium-high heat. If using wooden skewers, soak them in water for 20 minutes to prevent burning during cooking.
04 - Thread marinated lamb, red onion wedges, and bell pepper pieces alternately onto skewers, ensuring an even distribution.
05 - Place skewers on the grill and cook for 10 to 15 minutes, turning every 3 to 4 minutes until lamb is browned and cooked to preferred doneness.
06 - Remove from grill, arrange kebabs on a platter, sprinkle with chopped fresh herbs, and serve alongside lemon wedges.