First of all, the two onions are peeled and cut into 16th slices.
Heat the oil and fry the onion wedges in it.
In the meantime, wash and core the two peppers and cut into bite-sized strips. When the onion wedges start to color, add the pepper strips and fry until they are soft and also start to color.
Skim the onion and pepper mixture with a ladle and place in a plate, set aside.
Peel and finely dice the small onion and fry in the remaining oil.
Grate the small carrot and the piece of celery over the coarse grater. When the onions are translucent, add the shredded vegetables and fry them too.
Chop the leek into small pieces, peel the garlic, remove the seedling and chop.
When the vegetables are translucent, add the leeks, let them soften and then add the garlic. When it no longer smells raw, fold in the chopped tomatoes, mix in the tomato paste and water and season.
Bring the sauce to the boil, puree well and season to taste.
Now mix in the onion and pepper mixture.