Pour two cups of vegetable oil into a heavy bottomed saucepan and heat it over medium high heat.
Now put the onions, garlic and green peppers into the hot oil and cook for 30 minutes.
After having cooked the vegetables in the oil for half an hour, process them in the blender until you get a smooth paste (this should take about a couple of minutes), stopping and mixing the ingredients a couple of times.
Meanwhile, wash and core the tomatoes, removing the skins and seeds.
Put the cored tomatoes in the blender containing onion, garlic and pepper paste and pulse again until liquefied, about 30 to 50 seconds.
Now, pour the puree into the sauce pan and bring to a boil over medium high heat for 5 to 7 minutes or until you get the desired consistency, stirring occasionally.
To enhance the flavour of the spaghetti sauce add one large can of tomato paste and mix well.
Allow the sauce to cool to room temperature before pouring it into a plastic container. Store the spaghetti sauce in the refrigerator and use it to perk up not only spaghetti but also any other pasta dish.