Bouktouf is an Algerian vegan pureed soup made flavourful by the citrus taste of lemon and cilantro.
1. Heat the oil in a heavy stock pot over medium-high heat. Add the onions and sauté them slowly, until they are limpid, about 15 minutes.
2. Add the potatoes, zucchini, and tomato paste. Just barely cover with water, turn the heat to high, and cover. Once brought to a strong simmer, turn the heat down to medium-low.
3. When the potatoes are very soft and the zucchini has given itself to the soup, about 20 minutes, turn off the heat. Add the lemon juice and cilantro, and season to taste with salt.
4. Using a blender or food processor, purée the soup to a smooth consistency; working in batches, if needed.
5. Ladle in soup bowls.
6. Serve hot or cold.