Begin by preparing the chimichurri sauce. In a blender or food processor, blend garlic, vinegar, jalapeño, herbs, lime zest, and juice until smooth. Drizzle in olive oil until the sauce has the desired consistency. Continue blending for a full minute, stopping to scrape the sides of the work bowl if necessary.
Place the mixture in a bowl, season with salt and pepper, and let stand at least one hour before serving. Chimichurri will keep in the refrigerator for two days; just keep it covered.
Prepare the steak by trimming any excess fat and generously season with kosher salt and freshly ground black pepper. While you preheat your grill, let the steak come to room temperature.
Set up your grill for the direct/indirect method of cooking (one side very hot and other cooler). Allow sufficient time to fully preheat the grill to at least 400 degrees, preferably more.
Drizzle some olive oil on the steak, and sear each side until properly seared and delicious, about three minutes each side.
Move the steak to the grill's indirect side to finish cooking to an internal temperature of 130 degrees.
Remove the steak from heat, wrap in foil, and allow to rest for ten minutes.
Slice the steak against the grain and drizzle with the chimichurri sauce to serve.