Heat up olive oil, add chopped onion and cook for around 10 minutes.
Put cooked onion and a few spoons of tomato sauce in a blender and blend until it's smooth.
In another pot heat up some olive oil mixed with flour and sugar and stir for a few second.
When it gets a nice golden colour add the blended mixture, the rest of tomato sauce, water, salt and black pepper.
Bring it to a boil and then put in stuffed peppers.
Cook on a low heat for about an hour. (Make sure it's boiling a bit all the time.)