Cilantro & Chard Soup

Makes 4 main-course servings
3 tablespoons olive oil
2 medium onions, halved lengthwise, then thinly sliced crosswise
1 1/2 teaspoons salt
1/4 teaspoon turmeric
6 cups water
1/4 lb dried linguine, broken into 2-inch pieces (1 cup)
12 fresh chard leaves, stems and center ribs discarded and leaves coarsely chopped (8 cups)
1 (15- to 19-ounce) can kidney beans, rinsed and drained
1/2 cup finely chopped fresh cilantro
1tsp dill
1tsp parsley
Accompaniments: sour cream; lemon wedges

Heat oil in a 4-quart wide heavy pot over moderately high heat until hot but not smoking. Add onions and salt, then reduce heat to moderate and cook, stirring occasionally, until golden, 15 to 20 minutes. Reserve 1/4 cup onion.
Add turmeric to onions in pot and cook, stirring, 1 minute. Add water and bring to a boil. Add linguine and boil, uncovered, until tender, about 10 minutes. Stir in chard and beans and simmer, stirring occasionally, until chard is tender, about 5 minutes. Remove from heat. Stir in herbs, and salt and pepper to taste.
Serve soup topped with reserved onion.