Remove the Beef Tri-Tip (3 pound) the refridgerator and allow it to come to room temperature for 2 to 3 hours before cooking it.
Strip the leaves from the Fresh Rosemary (2 sprig) and chop them coarsely. Mince the Garlic (2 clove).
Zest and juice the Lemon (1). Combine the rosemary, garlic, lemon zest and juice and Coarse Sea Salt (1 tablespoon) in a blender or mortar and pestle, and blend or crush into a coarse paste.
Drizzle in enough of the Olive Oil (3 tablespoon) while continuing to grind the mixture with the pestle, until the mixture is thin enough to spread smoothly. Set aside.
Light a hardwood charcoal fire in a grill and place the grill rack about 4 inches from the heat.
When the flames have died down and the coals are glowing bright red, place the steak over the heat. Allow it cook, without moving it, until the underside is well browned, 10 minutes.
Turn the steak over and cook until the second side is well browned and the meat is rare. The steak is cooked rare when the thermometer reads 120 degrees F (50 degrees C) when inserted into the thickest part of the steak, close to the bone.
Transfer the steak to a carving board. Rub a generous amount of the chimichurri into both sides of the steak and let it rest 5 to 10 minutes before carving. If desired, serve with my preserved lemon chimichurri sauce from SideChef.