Wash vegetables and peel potatoes and onion (removing the inner green core if there is any).
Cut all the vegetables into irregular but small pieces, keeping all them separate.
Grease the bottom of a pan with olive oil, gently sauté the onion for two minutes.
Add the potatoes, cook for 3 minutes while stirring, then add the other vegetables and stir.
Add chopped tomatoes or tomato sauce, water, salt and oil. Do not overdo the sauce or tomatoes; fricandò is not "very red".
Cook for an hour, even an hour and a half, over low heat, stirring occasionally. If it gets too dry, add a little water. Conversely, if it is too slow, extend the cooking time.
Serve the fricandó warm, lukewarm, or at room temperature.