Cut the onion into small bits, peel and crush the garlic, rasp the ginger, remove the thyme leaves and finely chop the coriander.
In the empty frying pan (or large wok) fry the onion, garlic, thyme and ginger until the onion is clear and cooked.
Then add the cayenne pepper, chopped tomatoes, tomato puree and water. Simmer for 10 minutes.