Clean, wash and cut the peppers into small cubes. Scald tomatoes with hot water, skin them and chop them roughly. Peel and chop the onion. Chop the chillies. Fry everything together in hot oil.
Add sugar, salt and vinegar and bring to the boil. Simmer in open pot at medium heat for about 25 minutes. Stir several times in between. Season if necessary and let it cool down.