Place flat iron steak in a shallow casserole dish then rub with garlic and 2 tablespoons of olive oil. Cover with plastic wrap and refrigerate for 2-3 hours or overnight.

Combine the parsley, cilantro, garlic, jalapeno and olive oil in the work bowl of a food processor. Pulse until smooth. Add the lime juice and season with salt and pepper. Set aside at room temperature for an hour for flavors to come together.

Season the flat iron steak with salt and pepper. Grill over a hot fire for about 3-4 minutes per side for medium rare. Slice across the grain into thin slices and serve with the chimchurri sauce.