Combine all ingredients for the steak marinade in a resealable plastic bag. Add steak to marinade and reseal. Place on a plate or a casserole dish in case the bag comes unsealed. Place this in the fridge and marinate at least 4 hours, or up to 12.
Remove steak from marinade and preheat grill to 500 degrees. Discard marinade. Add steak and grill 5 minutes, covered. Flip. Grill 3-4 minutes on second side.
Remove steak from grill and place on a plate. Cover with foil. Let rest for about 10 minutes.
While the grill is coming to temp, add all ingredients for the chimichurri into a food processor fitted with an "S" blade. Pulse until chimichurri reaches your desired consistency, scraping sides if necessary.
Slice steak against the grain and place on serving platter. Top with chimichurri. Serve.
Notes
Only flip these steaks once. This is important to keep it covered and let the grill do its thing so the heat doesn't escape.Slicing "against the grain" simply means look for lines in the beef that run line lines on hardwood floors. These lines are typically from end to end, lengthwise. Slice perpendicular to those lines. It does drastically effect the tenderness and quality, believe it or not.WHATEVER YOU DO, DO NOT BE TEMPTED TO SKIP THE RESTING PHASE. The juices in meat are at boiling temp when coming off the grill. If you slice into it too early, the juices will drain out all over the plate and you'll have a tougher and drier end product. The resting allows the juices to cool and redistribute so they end up in your mouth, not all over the platter.