When it comes to nutrition, this is no lightweight. Swiss chard contains betalains (also found in beets), vitamins A, C , E and K, magnesium, potassium, fiber, calcium, choline, a host of B vitamins, zinc and selenium.
2 teaspoons olive oil
2 cups thinly sliced onion
8 cups torn Swiss chard (about 12 ounces)
1 teaspoon Worcestershire sauce
1/4 teaspoon salt
1/8 teaspoon black pepper