Prepare the Kettle for direct cooking over medium heat (180°C to 230°C) or use medium heat on a stove top.

Place a small Weber Casserole Dish over direct medium heat. Add the oil and onion. Sauté for 3 minutes, or until the onion has softened. Add the garlic and continue to cook for a further 2 minutes, or until the onion and garlic are just starting to colour. Add the remaining ingredients. Bring to a simmer and cook for 10 to 15 minutes, stirring as necessary, until the sauce is starting to thicken and has reduced by half.

If desired, once the sauce has cooled, process in a blender until smooth.