Gas-Grilled Argentine Steaks with Chimichurri Sauce

For the Sauce: Combine hot water, oregano, and salt in small bowl; let stand 5 minutes to soften oregano. Pulse parsley, cilantro, garlic, and red pepper flakes in food processor until coarsely chopped, about ten 1-second pulses. Add water mixture and vinegar and pulse briefly to combine. Transfer mixture to medium bowl and slowly whisk in oil until incorporated and mixture is emulsified. Cover with plastic wrap and let stand at room temperature at least 1 hour (if preparing sauce in advance, refrigerate and bring to room temperature before using).

For the Steak: Combine cornstarch and salt in small bowl. Pat steaks dry with paper towels and place on wire rack set in rimmed baking sheet. Rub entire surface of steaks with cornstarch mixture and place steaks, uncovered, in freezer until very firm, about 30 minutes.

Turn all burners to high and heat grill with lid down until very hot, about 15 minutes. Scrape cooking grate clean with grill brush.

Season steaks with pepper. Place steaks on grill, cover, and cook until steaks begin to char, 2 to 3 minutes. Uncover grill, flip steaks using tongs, and cook on second side until beginning to char, 2 to 3 minutes. Flip again and cook first side until well charred, 2 to 3 minutes. Flip 1 last time and continue to cook until second side is well charred and instant-read thermometer inserted into center of steak registers 115 degrees for rare, about 2 minutes, or 120 degrees for medium-rare, about 4 minutes. Transfer to large plate and let rest, loosely tented with foil, for 10 minutes. Slice steaks crosswise and serve, passing chimichurri sauce separately.