Flat Iron Steak - Parmesan Pepper Sauce

Instructions
Pour 1/4 cup dressing over steak and seal in a Ziploc bag.
Combine sour cream, 2 tbsp of the remaining dressing, Parmesan cheese, pepper and salt. Refrigerate until serving time.
Heat remaining 2 tablespoon dressing and garlic in large nonstick skillet on medium heat. Add onions; cook until golden brown, stirring often. Remove onions; set aside.
Drain steak; discard marinade. Cook steak in same skillet on medium heat 3-4 on each side for medium doneness. Place on cutting board; slice crosswise into thin strips. Serve steak topped with sauce and onions.

Ingredients

1lb flat iron steak
1⁄2cup zesty Italian dressing, divided
1⁄3cup sour cream
4 1⁄2teaspoons parmesan cheese, grated
3⁄4teaspoon course black pepper
1⁄4teaspoon sea salt
2garlic cloves, chopped
1large onion, thinly sliced