For the tomato sauce,
place all ingredients in a saucepan and simmer over medium to low heat until thick, about 25 minutes. Crush the sauce with the back of a fork to break up any large pieces of tomato. Season to taste and set aside.
For the nutballs, preheat oven to 180°C. Heat 1 tablespoon of oil in a frying pan and add the onions and garlic and cook over a medium heat until soft and golden. Place in a large bowl and allow to cool slightly before adding remaining ingredients. Stir thoroughly to combine and, using tablespoons of mixture, shape into balls, you will have around 15. Place each ball on a large plate or tray and set aside.
Heat the remaining oil in a large frying pan over medium high heat. Place the nutballs in a single layer in the pan and carefully turn, browning on all sides. It may be necessary to do this in batches. Place the balls in a single layer in an ovenproof dish and pour over the tomato sauce. Place in the oven and cook for 10 minutes, until the sauce is bubbling, and the balls are cooked through.
Serve with extra grated cheese over the cooked spaghetti.