Combine the marinade ingredients and place with the steak in a ziplock bag or glass bowl. Be sure to get marinade onto all of the steak surfaces.
Marinade for at least 2 hours, overnight if you can.
Combine the chimichurri ingredients in a food processor.
Process everything but the olive oil, and then add the oil in a steady stream to combine.
Taste and adjust for salt and pepper, and then refrigerate overnight.
Heat your grill to ~500 degrees F.
Remove the steak from the marinade and grill the steak for 7 minutes on each side.
When done, serve the whole steaks dressed with the chimichurri.
Or, slice the meat thinly against the grain and serve the steak with the chimichurri on tortillas.