Mist a small pan with low calorie cooking spray, then fry off the garlic, shallot and chopped chilli until they have started to colour slightly.
Pour in the white wine vinegar, then add the sweetener, salt and tomato puree. Stir well and bring to the boil.
Stir in the honey, allow to simmer for a minute then remove from the heat.
Add the xanthan gum a sprinkle at a time, whisking well after each addition. Continue adding and whisking until the sauce has thickened to the right consistency. Check the taste and add a little more sweetener if necessary.
Remove from the heat and allow to cool, then pour into an airtight jar or bottle and keep in the fridge until you're ready to use.