Purple potatoes combine with South American flavors for an exciting main-dish salad. Boiling the potatoes whole allows them to retain their brilliant color; letting them stand before they're cut "sets" the color.
To prepare beef, combine first 6 ingredients in a large zip-top plastic bag. Add steak to bag; seal. Marinate in refrigerator 1 hour, turning occasionally.
To prepare the vegetables, place potatoes in a saucepan; cover with water. Bring to a boil. Reduce heat; simmer 20 minutes or just until tender (do not overcook). Drain and let stand 30 minutes. Quarter potatoes lengthwise. Combine the potatoes, corn, bell pepper, celery, and onions in a large bowl.
To prepare dressing, combine 3 tablespoons juice and next 5 ingredients (3 tablespoons juice through hot sauce), stirring with a whisk.
Remove steak from bag; discard marinade. Place steak on a broiler rack coated with cooking spray. Broil 6 minutes on each side or until desired degree of doneness. Let stand 5 minutes. Cut steak in half lengthwise. Cut each half diagonally across grain into thin slices. Add steak to potato mixture. Drizzle with dressing; toss well to coat. Sprinkle with cilantro.