Wash and halve the tomatoes. Peel the red onion and cut into quarters.
Put the tomatoes, unpeeled garlic cloves, onion and thyme sprigs into a roasting tin. Season with a large pinch of salt, the sugar and a good grind of black pepper. Drizzle with the oil and roast in the oven for 30 minutes.
Meanwhile, boil a kettle and make up the stock according to the packet instructions.
Remove the roasting tin from the oven and leave for a few minutes to cool slightly.
Mash the garlic with the back of a fork, and discard the skin.
Blend the roasted vegetables and stock in a liquidiser or with a hand-held stick blender until smooth.
Homemade tomato soup is easy and worth every bit of the effort which, let's be honest, isn't much!