Grate and Mix the Meat

Begin by coarsely grating the onion using a box grater placed directly on the cutting board. To extract excess moisture, wrap the grated onion in a clean kitchen towel or pass it through a fine-mesh sieve. Once the liquid has been discarded, transfer the onion to a large mixing bowl. Add the ground beef, sumac, and baking soda to the bowl. Season generously with 2 to 3 teaspoons of salt, and thoroughly combine the ingredients. It is crucial to work the mixture until it becomes sticky and cohesive. To check the seasoning, cook a small portion of the mixture in a pan before finalizing the seasoning. Cover the bowl and refrigerate the mixture for at least 1 hour to allow the flavors to meld.

Form the Koobideh on Skewers

Prepare a charcoal grill by lighting it in advance. Divide the meat mixture into six equal portions and shape each into a ball. Use long metal skewers (12 inches or longer) that are at least ¾-inch wide to hold the meat. Wet your hands to prevent sticking, and gently press each portion of meat around the skewer, shaping it into long, flat koobideh that measure about 10 inches in length and ½-inch thick. To ensure even cooking, use your thumb and index finger to create shallow indentations along the length of the meat. Pinch the ends of the meat around the skewer to secure it. If skewers are unavailable, the meat can be shaped into 6-inch patties and arranged on a parchment-lined baking sheet for oven cooking.

Cook the Koobideh

For grilling, remove the grill grates and heat the charcoal to a high temperature. Suspend the skewers over the heat source, with the tips resting on the grill. Alternatively, lay two metal pipes parallel to one another on the grill to prevent the koobideh from sticking. Turn the skewers every 30 seconds for 2 to 3 minutes, ensuring even cooking, then continue grilling for an additional 3 minutes until the meat is charred and fully cooked. For oven baking, preheat to 500°F (260°C). Place the skewers on a sheet tray and cook for about 7½ minutes before flipping. Continue baking for another 7½ minutes, until the koobideh is golden brown and crispy on all sides.

Serve and Garnish

Once cooked, remove the koobideh from the skewers. Place the skewers on a platter, covering them with lavash to help easily slide the meat off. Brush the koobideh with melted butter and sprinkle additional sumac on top. Serve with lime wedges for a zesty finish, if desired.