Spray a frying pan with low calorie cooking spray and cook the onions and garlic until the onions are soft.
Add the tomato puree and tinned tomatoes and cook for 5 minutes on high, stirring frequently.
Add in the rest of the ingredients, lower the heat and simmer for 20 minutes, the sauce should thicken nicely.
If the sauce seems a bit too thick just add a tiny bit of water and stir well.
You can use this sauce as it is or if you prefer a smoother BBQ sauce just blitz it in a food processor until you get the desired consistency.
You can make this in advance, just put it in a sterilised airtight container and store in the fridge until ready to use.