Chop the leeks and braise them in a little oil until softened. Meanwhile, grate the tomatoes, add them to the ready leeks.
Let simmer about 10 min. until some of the water evaporates. Add a pinch of sugar, chopped parsley, salt to taste and stir. Transfer mixture to a tray.
Stir and fill the peppers. Put the peppers in with the tomato sauce and cover with foil. Bake 30 min., remove the foil and bake another 10 min. or so. Sprinkle the ready stuffed peppers with parsley.