This hearty salad features pesto made of walnuts and peppery watercress leaves'a savory twist on the classic basil-pine nut version'with more chopped cress, lean ham, and lima beans tossed in a lemon and yogurt dressing.
Cook pasta in a large saucepan of lightly salted boiling water for 9 minutes. Add the beans and return to a boil, then reduce the heat slightly and cook for 2 to 3 minutes until pasta is tender and the beans are cooked but still firm.
Meanwhile, mix together the tomatoes, ham, chives, and oil in a large serving bowl. Set aside. To make the pesto, process the watercress, walnuts, and garlic together in a food processor or blender until finely ground. Add half the oil and pulse until combined, then add the remaining oil, lemon zest and juice, and the yogurt and blend again. Season to taste with salt and pepper.
Drain the pasta and beans and immediately add them to the tomato mixture. Mix well, then cover and let stand for 5 minutes. Stir the pesto and chopped watercress into the salad and serve immediately.