How to Make It
Prepare the chimichurri, combine the herbs and garlic in a food processor and finely chop. Add the oil, vinegar, water, hot pepper flakes and salt and pepper and process until a thick sauce forms; the chimichurri should be highly seasoned. Pour one fourth of the chimichurri into a baking dish just large enough to hold the meat.
Holding the knife parallel to the cutting board, cut the tenderloin lengthwise into 4 flat, even slices. Place each slice between two sheets of plastic wrap and pound to a thickness of 1/4-inch. Arrange the steaks on top of the chimichurri in the baking dish. Pour another quarter of the chimichurri on top. Marinate the meat for 30 minutes to 1 hour.
Set up the grill for direct grilling and preheat to high. Arrange the beef slices on the grate on the diagonal and grill until cooked to taste, about 2 minutes per side for medium-rare, rotating the slices 90 degrees after 1 minute to create crosshatched grill marks. Transfer the churrasco to plates or a platter and serve the remaining chimichurri sauce on the side.