Place the tomatoes, onion and peeled garlic cloves in an oven proof dish. Bake for 30-35 minutes until the veg begin to char at the edges. Keep an eye on the garlic. If it looks like it’s beginning to brown, cover it with some of the other veg.
Place the cooked vegetables, any liquid from the oven dish and the remaining ingredients into your food processor. Whizz until blended to your desired consistency.