Lentil Soup and Broccoli Rabe

2 tablespoons cooking oil
1 onion, chopped
2 carrots, chopped
2 rib celery, chopped
1 clove garlic, minced
2 cups lentils
2 1/2 quarts water
2 tablespoons tomato paste
1 bay leaf
2 1/4 teaspoons salt
1/4 teaspoon ground black pepper
1 pound broccol rabe, cut in 1 1/2 inch pieces
zest of 1 1/2 lemons, grated

Cook the broccoli rabe in a separate pan, not in the soup pot. That way, any excess bitterness from the vegetable goes down the drain with the cooking water rather than into the soup. 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. Serves 4.

VARIATIONS: * Omit the broccoli rabe. Shred ten ounces of raw spinach, escarole, or Swiss chard leaves and stir them into the soup five minutes before it's done.