Saucepan, food processor, strainer
Blanch tomatoes in boiling water for 30 seconds. Peel, reserving the skins, then cut tomatoes in half. Squeeze pulp and seeds from tomato halves over a bowl so just the flesh remains. Reserve all.
Heat oil in a saucepan until hot then add tomato flesh, onions and garlic. Cook for 5 minutes. Add sugar, tomato paste, cumin, curry powder, chilli flakes, salt, pepper and stock. Simmer for 30 minutes.
Transfer to a food processor and blend until smooth. Strain and discard any solids.
In a saucepan bring reserved tomato skin, seeds and pulp to the boil and simmer for 10 minutes. Strain and discard solids.Return liquid to the saucepan and add balsamic. Reduce until syrupy. Serve soup hot or chilled, drizzled with tomato and balsamic syrup.