Place the meat in a plastic gallon freezer bag and add the garlic, salt, oregano, vinegar, and olive oil. Seal the bag and massage the ingredients together and into the meat. Marinate in the refrigerator for at least 4 hours up to overnight.

To make the chimichurri sauce: Finely mince the parsley, oregano, green onions, and garlic. Combine them in a medium bowl with the red pepper flakes, olive oil, vinegar, and lemon juice. Mix well and season with the kosher salt and add more to taste. Make a day ahead and store in the refrigerator until ready to serve.

Preheat the grill to high. Pull the steaks and allow them to rest at room temperature for 30 minutes. Pull the steaks from the marinade and place them on the hot grill. Baste the steaks with the remaining marinade and grill for 3-5 minutes on each side for medium rare, or until steaks come to 125°F. Transfer to a plate or cutting board and rest for 10 minutes.

While the meat is resting, place the tomatoes and onion in a medium-sized bowl and add two heaping tablespoons of the chimichurri sauce. Gently toss to coat and transfer to a serving platter.

Slice the steak across the grain and pile it on top of the tomato salad. Drizzle with generous amounts of the chimichurri sauce, and pass at the table for more.