The problem I found with a lot of recipes is that they use tinned tomatoes and chopped onions which is fine but then you need to blend it and that can be a pain. This way you just add everything together and simmer. I buy my white balsamic in Lidl it's less than a pound and by using the white one it keeps the lovely red colour. I also buy the garlic and onion granules at the supermarket (I got mine in ASDA) and it works out quite economical and as a bonus you know exactly what is in it couldn't be easier and you can save your 'syns' for something else yummy : )
Syn free on all plans
2 tsp onion granules
1 tsp garlic granules
500g pack of passata
2 tsp celery salt
1 tsp english mustard powder
1 tsp ground white pepper
2 tbsp sweetener (like splenda)
150ml white wine vinegar
100ml white balsamic vinegar (see notes above)
1 tbsp worcestershire sauce
Just add everything together in a saucepan, Bring to a boil then reduce the heat and simmer on a low heat for 20-30 minutes until sauce is thick and reduced.
Syn free and makes about 250ml of ketchup and will keep in the fridge for a few weeks.