Start the sauce so that it can simmer while you prep everything else. Heat oil in a saucepan and saute onions, garlic and carrots. Once the onions are soft, add tomatoes, tomato puree, water, thyme, oregano, sugar, salt and pepper and let this come to a boil. Then reduce the heat to a simmer and simmer for 20-25 minutes till the tomatoes break down and the sauce is thick.