Zucchini-Buttermilk Soup With Watercress Pesto

Ingredients

• Soup:
• Cooking spray
• 1/2 cup chopped leek
• 1/2 cup chopped celery
• 5 cups chopped zucchini (about 1 1/4 pounds)
• 1 (14-ounce) can fat-free, less-sodium chicken broth
• 1 cup fat-free buttermilk
• 1/2 teaspoon salt
• 1/4 teaspoon freshly ground black pepper
• Pesto:
• 1/2 cup watercress leaves
• 2 tablespoons grated fresh Parmesan cheese
• 1 tablespoon pine nuts
• 1 tablespoon fresh lemon juice
• 1 to 2 tablespoons water
• 1 1/2 teaspoons extravirgin olive oil