In a large bowl, combine the ground beef, chopped onion, parsley, garlic, cumin, coriander, paprika, cinnamon, salt, black pepper, and cayenne pepper if using. Mix well until all ingredients are evenly incorporated.
Divide the mixture into 8 equal portions. With damp hands, shape each portion into a long, oval-shaped kebab around a skewer, pressing firmly to ensure they hold together.
Preheat your grill or grill pan over medium-high heat. Brush the kebabs lightly with olive oil to prevent sticking.
Place the kebabs on the grill and cook for about 4-5 minutes on each side, or until they are browned and cooked through, reaching an internal temperature of 160°F.
Remove the kebabs from the grill and let them rest for a few minutes before serving.