2. Add the broth to a soup pot, bring it to a boil and add the zucchini.
3. Reduce the heat and simmer, covered, for 4 to 5 minutes, or until the zucchini is barely tender and still bright green. Remove from heat and cool.
4. Meanwhile, heat the oil in a small, non-stick frying pan. Add the onion, chili pepper, fennel, cinnamon and cumin and saute until onion is soft, but not brown and spices are fragrant.
5. Put both the zucchini and spice mixture into a food processor and pulse until well chopped but still retaining texture. Pour into a bowl and stir in the buttermilk and season to taste with salt and pepper.
6. Chill for at least 2 hours. Serve garnished with a sprinkling of cilantro and a few added drops of lemon or lime juice to taste.