In small bowl, mix together tomatoes, onions, parsley, olive oil, vinegar, garlic, oregano, Adobo and pepper flakes; cover and refrigerate for at least 1 hour, or up to 48 hours.
Heat grill to medium-high heat. Sprinkle steak on both sides with Adobo. Cook, flipping once, until steak is well browned on both sides and cooked to desired temperature (about 6 minutes for medium-rare). Let rest for 5 minutes.
Divide steaks evenly among serving plates. Top with reserved Salsa Criolla.
Salsa Criolla, the classic, fresh Argentinean sauce of chopped tomatoes, onions, parsley and red wine vinegar, is traditionally paired with grilled skirt and flank steaks. However, if you’re looking to perk up the flavor of simply grilled chicken, fish fillets, shrimp or scallops, top with Salsa Criolla, and taste how this fresh sauce transforms any main course into a mouthwatering feast!