Heat the oven to 200°C/180°C/Gas 6. Arrange the tomatoes on a baking tray. Halve any large tomatoes. Roast for 30 mins till the tomatoes are soft and charred.
While the veg roast, halve the onion. Peel and dice it. Peel your carrot. Finely dice it. Finely dice the celery.
Set a pan over high heat. Add 1/2 tbsp oil. Stir in your veg and season with salt and pepper. Gently fry for 5-8 mins till the veg have softened.
Crumble in the stock cub and pour in 700ml boiling water. Pop on a lid. Simmer for 15 mins.
Tumble the tomatoes, onion and any juice for the tray into a blender. Add a peeled 1cm thick slice of the ginger and the veg and stock from the pan with 1 tbsp of the tamari. Whizz till smooth (or you can tip the tomatoes into the pan and use a hand-held blender to blitz the soup).
Ladle the soup into warm bowls and drizzle with 1 tsp tamari each before serving.