6 sweet potatoes
1/4 cup butter
1 small onion, minced
1 tablespoon packed brown sugar
3/4 tablespoon orange zest
3/4 teaspoon salt
1/4 teaspoon ground cumin
1/4 teaspoon ground cinnamon
1/4 teaspoon ground black pepper
1/8 teaspoon ground allspice
1/4 cup sour cream
2 tablespoons chopped fresh cilantro
2 egg whites