Clean and wash the celery and cut into narrow strips. Heat the olive oil in a large saucepan, add the cut celery and sweat briefly in the oil. Pour the vegetable stock extract over it and deglaze with water, whereby the liquid level in the pot should be about 1 - 2 cm high. Then add the canned tomatoes. Season with salt, pepper, coriander and lemon juice and stir in the tomato paste.
Close the pot with a lid and let the side dish simmer over medium heat for approx. 15 - 30 minutes until the celery is firm enough to bite. A millet dish tastes good with it.