Melt butter in heavy saucepan over medium heat. Add bulgur wheat, salt and pepper. Sauté, stirring constantly, until butter is light amber and foams. Stir in broth and tomato paste. Bring to boil. Cover. Lower heat. Simmer 30 minutes or until wheat is tender and all liquid is absorbed. Let stand, covered, 15 minutes before serving. Top each serving of bulguri with a dollop of yogurt, if desired.