Mix together the kosher salt, black pepper, garlic powder, Piment d'Ville, onion powder, dried rosemary and cayenne. Rub the seasoning mix all over the tri-tip, then let the meat sit at room temperature for 30 minutes.
Gas grill: Preheat the grill to medium-high, leaving 1 to 2 burners off to create an area with indirect heat.
Charcoal grill: Bank warmed coals on one side of the grill to create an area with indirect heat.
Grill the tri-tip slowly over indirect heat, flipping once to cook evenly. Once an instant-read thermometer reads 115°F (46.1°C) in the middle of the steak, move it to direct heat and continue grilling for 2 minutes per side, until charred and cooked to 125°F (51.6°C). Remove from the grill and allow the tri-tip to rest for at least 10 minutes before slicing–it will continue to cook to a medium-rare temperature.
Meanwhile, whisk together the parsley, cilantro, olive oil, red wine vinegar, honey, lemon juice and grated garlic. Season to taste with salt and pepper.
Once the tri-tip has rested, slice it against the grain. Top with chimichurri to serve.