Lentil Soup with Broccoli Rabe

In a large saucepan, heat the oil over moderately low heat. Add the onion and cook, stirring occasionally, until translucent, about 5 minutes. Stir in the carrots, celery, and garlic and cook, stirring occasionally, until the vegetables start to soften, about 5 minutes.

Stir in the lentils, water, tomato paste, bay leaf, salt, and pepper. Bring to a boil. Reduce the heat and simmer, partially covered, stirring occasionally, until the lentils are tender, about 30 minutes.

Meanwhile, in a large pot of boiling, salted water, cook the broccoli rabe until just tender, about 5 minutes. Drain.

Stir the lemon zest into the soup. Remove the bay leaf. Ladle the soup into bowls and top each serving with some of the broccoli rabe.