Cut the meat in 2 cm dices, peel the onions and cut half of them in rings and finely chop the other half.
Wash the bell peppers and cut in 2 cm length pieces.
Put meat, onion rings, finely chopped garlic, bell pepper powder, oregano, white pepper and oil in a bowl and mix well and marinate it for 5 hours. Best over night in the refrigerator.
Put meat, onion rings and bell pepper on a skewer, place on hot grill and roast from all sides.
If needed season with salt and serve with the chopped onions.