Whisk all ingredients together. To thicken sauce, heat in a small saucepan on a low heat for about 20 minutes.
Store in an airtight container in the fridge for about 2 weeks. Suitable for freezing.
If you don't have the time you can just blitz this sauce and not cook it. The sauce won't be quite as rich and thick. If you don't have Sugar Free Tomato Sauce, switch for tomato passata. but note that the recipe won't be quite as rich as it would be by using tomato sauce.As the recipe doesn't use any emulsifiers, it may separates slightly. Just whisk it slightly to bring it back together.