Roasted Sweet Potato Salad with Barley and Arugula

Heat oven to 450 degrees F. In a medium saucepan, combine the barley, 2 1/2 cups water and 1/2 teaspoon salt and bring to a boil. Reduce heat and simmer, covered, until the barley is tender, 20 to 25 minutes. Drain off any remaining water in the pan and spread the barley on a baking sheet to cool. Meanwhile, on a second baking sheet, toss the sweet potatoes with 3 tablespoons oil, 1/2 teaspoon cumin and 1/2 teaspoon each salt and pepper. Roast until golden brown and tender, 15 to 18 minutes. In a large bowl, whisk together the lime juice, remaining 1 1/2 tablespoon oil and 1/4 teaspoon cumin, pinch cayenne and 1/4 teaspoon salt. Add onion, toss and let sit, tossing occasionally, for at least 5 minutes. Add the barley to the bowl and toss to combine. Gently fold in the sweet potatoes, then the arugula and mint. Serve with feta, if desired.