Place all ingredients in a large saucepan and bring to the boil, stirring.
Simmer for 3 hours, covered and stirring from time to time.
Watch the video above in the post to see the consistency of the tomato sauce once cooked. If the sauce hasn't achieved the desired consistency, continue to simmer uncovered until it reaches the preferred consistency.
Strain half of the mixture through a coarse sieve into a bowl, and then the other half. Use a spoon to push sauce through the sieve and extract as much liquid as possible. Discard solids.
Pour hot mixture into a medium-sized sterilised bottle and seal.
Store in a cool and dark place. Once opened, store in the fridge.
Makes 400–500 ml. Double, triple or increase quantities in recipe to make a larger batch of sauce.