Peel and coarsely chop the onion, then pulse in a food processor with the steel blade until very finely chopped.
Add the ground beef to the food processor with the chopped onion, Sadaf seasoning, Spike seasoning (if using), and water.
Process until the mixture is evenly combined and the meat is finely ground and cohesive.
Transfer the seasoned meat to a lidded container and refrigerate at least 2 hours or up to all day to firm and allow flavors to meld.
Preheat a gas or charcoal grill to high and oil the grates by wiping with a paper towel dipped in olive oil.
Form the chilled meat into long, cylindrical kabob shapes around skewers, using two skewers per kabob if they are thin to prevent spinning.
Reduce heat to medium-high, place the kabobs on the grill, and cook 4–5 minutes on the first side until they release easily and have browned grill marks.
Rotate each kabob to create criss-cross marks and cook an additional 3–4 minutes, then turn and finish cooking until the internal temperature reaches 160°F (about a total of 15 minutes, depending on thickness and grill temperature).
Remove kabobs from the grill and serve hot.
