Let's start! Wash and pat dry the fish and set them aside. In a wide bottom pot fitted with a lid, add the olive oil and heat on medium heat. Chop the onions finely and add them to the pot and stir. Keep stirring occasionally until the onions have become soft and a little golden. Slice the garlic in thin thin slices and add. This is the time where you will add the green chilly if you want a little kick. Stir and fry for one 30 more seconds. Add the tomato sauce, the salt and pepper and stir again. Add the water and bring the heat to high. Bring to a boil and reduce the heat to medium low and cover with the lid. Let the sauce simmer for 10 minutes. After 10 minutes add the fish in the pot. With a spoon add some sauce on top of the fish and cover. You will not stir with a spoon anymore. Put the lid back on. Occasionally, you will shake the pot so the sauce goes on top of the fish and the fish don't get stuck at the bottom of the pot. Cook for 15 minutes with the lid on and uncover and cook 5 more minutes on medium low heat all the time. You will see the sauce will have thickened at the bottom. Once it does remove from the heat and let it rest for 5 minutes before serving. Serve warm with lots of fresh bread! Enjoy!