1. Blend soy sauce, vinegar, syrup, garlic, salt, and pepper in a blender until smooth.
Toss steaks with mixture.
Marinate at room temperature, minimum 15 minutes.
Sear the steak on a hot grill or cast iron pan on both sides until there is a nice char on each side. Finish cooking to desired doneness in oven or on low on the grill.
•For the chimichurri sauce: In a food processor add the parsley, cilantro, red onion, vinegar, and garlic. Pulse until combined but still a bit coarse, about 10 pulses. Add the crushed red pepper, lemon juice, and then slowly drizzle in the oil, pulsing about 5 more times. Season with salt and pepper and set aside for the flavors to meld.
The chimichurri can be made up to three days in advance.