I'll second the butter, onion, and tomato sauce. It is really very rich. I only make it occasionally.
I had the tomato sauce today with pasta and a salad also from Hazans book. Take a clove of garlic, rub it on a bread crust and toss into a bowl. top with shredded savoy cabbage. seal for an hour. discard bread and garlic. serve with vinaigrette. I like this salad and it pairs well with the rich tomato sauce.