The Keyma: Mix the meat, salt and pepper with bulghour and knead like a dough, adding a little water from time to time. Keep kneading for 20 minutes until the mixture is like a medium soft dough. Dip hand in cold water and make balls the size of a walnut. Then make a dent in the middle with your thumb and press all around the inside wall to make a round opening for the filling. The thinner the wall the more successful your kufta will be. Place the filling in this hole and bring open edges of the kufta together sealing and smoothing the surface with wet fingers. Flatten the roundness of the kufta slightly by pressing gently between the palms.
Filling: Fry meat on medium fire until the fat lets itself loose stirring occasionally, add onions and cook on slow fire for 30 minutes, stirring frequently. Then add green pepper, parsley and cook 10 minutes more. Add the rest of the ingredients and cook 5 minutes longer. Chill in the refrigerator. This could be prepared a day ahead. Shape the chilled filling into balls the size of a large marble to fill the inside of the meat balls, or put a teaspoonful of the filling into the balls.
The Broth: Make broth by boiling the soup bone in salted water. Remove scum and strain. Add tomato sauce if desired. Drop kuftas, a few at a time in the boiling broth, cover and cook for 8-10 minutes, by then the kuftas will come up to the surface. Use a strainer spoon to remove kuftas so as not to puncture the balls. Serve immediately with or without the broth.
If any meat and bulghour mixture is left over, shape into small patties and boil in broth same way as the kuftas. This patty, when cold may be cut in half, dipped in egg and fried.
Do not leave kuftas in broth except when serving.
To heat the left over kuftas the next day, drop them again in boiling broth or plain tomato and water mixture for a few minutes.