Combine ground beef, grated onion, sumac, salt, ground black pepper, and turmeric in a mixing bowl.
Knead the mixture for about 5 minutes until it is cohesive and can be molded easily.
Set aside kebab mixture. While preparing grill.
Divide the kebab mixture into 8 portions. Dampen your hands water.
Take a portion of the mixture and roll it into a sausage shape of 4 to 5 inches long.
Holding meat in one hand, press the thin edge of the sword-like skewer into the lump, simultaneously wrapping the meat around the middle section of the skewer by squeezing it all around.
Continue to squeeze the meat gently unto the skewer, gradually spreading and molding it into a 7 to 8 inches long kebab that is snugly and evenly held all around the skewer. The kebab thickness should be about 2/3 inch.
Sprinkle a few drops of onion juice over the kebabs before placing on the grill.
Place skewers on hot grill without directly touching the grill. Within a few seconds, start flipping the skewers over. This helps cook the meat on the outside and attach it to the skewer. It is important to flip them over before they cook too much on one side, or the meat on the other side will fall off.
Continue to flip Kebabs often. Kebabs should be complete in 7 to 10 minutes
Brush the basting mixture just before taking the kebabs of the grill