Peel and de-seed the tomatoes, discard the tomato skin.
Chop up the tomatoes placing the flesh onto a chopping board. Cut the flesh into small 1cm chunks.
Place the seeds and core of the tomatoes into a fine sieve and place the sieve over a bowl. Using a spoon, press the tomato seeds and core to extract as much juice from the tomatoes as possible. Set the juice aside for later and discard the seeds.
In a large saucepan, heat the olive oil over a medium heat. Add the onion to the pan and cook gently for 5 minutes, taking care to cook, but not colour the onion. Add the crushed garlic to the pan and cook for a further minute.
Add the chopped tomatoes, tomato juice, tomato passata, vegetable stock and sugar to the pan and cook over a medium heat for 10 minutes.
Season the soup with salt and pepper and check for taste. Now add the shredded basil to the soup, stir through and serve.