2 pounds flatiron steak or beef skirt steak
Kosher salt and freshly ground black pepper, divided
1 large white onion, thinly sliced into rings
4 plump garlic cloves, minced
Freshly squeezed juice of 2 limes
1 tablespoon olive oil
Handful of cilantro leaves
Cut steak into 4 to 6 equal pieces and season with salt and pepper.
Place steak in a large resealable plastic bag. Add onions, garlic and lime juice. Seal bag, pressing out air. Squish everything together to coat steak. Place bag in a dish, refrigerate and marinate at least 1 hour and up to overnight.
Remove steaks from bag and reserve marinade. Scrape off garlic sticking to meat. Season meat again with salt and pepper.
Heat a large heavy skillet over high heat until nearly smoking. Swirl in oil. Add steaks and cook about 4 minutes per side for skirt steak and 6 to 7 minutes per side for flatiron steak, turning once for medium-rare.
Transfer steaks to a platter, cover loosely with foil and let rest.
Add reserved marinade, onions and garlic to skillet. Cook, stirring often, adding a tablespoon of water if pan gets dry, until onions are tender, 8 to 10 minutes.
Carve steak into thin slices. Serve with onions and sprinkle cilantro on top. Serve at once.
Makes 4 to 6 servings