02Purée the soup with an immersion blender or a food mill or in batches in a blender, taking care to remove the lid or take out the center insert and to cover with a towel to avoid hot splashes. Return to the pot, heat through, add pepper and cayenne to taste and stir in the lemon juice. Serve, garnishing each bowl with paper-thin slices of zucchini, chopped chives and croutons if desired.