I make my own sauce. I buy passata ( tomato purée) brand I use is pomi (I get it from an Italian deli).
Put some olive oil in a sauce pan, 2 cloves of garlic, and chopped onion. Put on medium heat andFry off the onion until see through. Next, add the passata ( I put 3 cartons in as I make a bit extra) salt, pepper and some basil and also add around 300/400 ml of boiled water. Give a good stir. Cook until it boils then lower the heat and simmer for a good 2 hours, stirring every so often.
After, that it's ready! If you have any left over, leave until completely cold, put in fridge, good enough for about a week xxx