1. Bring 3 cups water to a boil in large saucepan over high heat. Add lentils, and reduce heat to medium low. Cover, and simmer 15 minutes, or until lentils are just tender. Drain well. Spread lentils on large baking sheet to cool.
2. Toss lentils, carrot, green onions, celery, bell pepper, cilantro, parsley, garlic and lemon zest in large bowl. Drizzle with lemon juice and olive oil, and toss to coat. Season with salt and pepper. Spoon salad into bowls lined with lettuce leaves.