1. Cook onion in hot oil in a cast-iron or large skillet over medium heat about 4 minutes or until onion is tender. Stir in ground beef and next 6 ingredients, and cook, stirring occasionally, 15 minutes or until beef crumbles and is no longer pink.
2. Spoon beef mixture on bottom halves of toasted buns; top with about 3 tablespoons Cilantro Slaw and remaining bun halves. Serve with remaining Cilantro Slaw.