Cut the meat and onion into larger chunks. Add salt and onion, then mash with your hands, until it releases its juice. The lamb is seasoned with crushed pepper and cumin, then add onions.
Add oil and vinegar, stir well, salt as needed. Allow the meat to marinate in refrigerator for about 1 hour.
Thread the meat on the skewer. Place to cook on the grill for about 6-8 minutes on each side.
Serve lamb skewer with a side of vegetables.