Remove the tri-tip from the refrigerator 30-45 minutes before grilling to allow it to come to room temperature. Using a sharp knife, cut small slits across the top of the roast, about ½-inch deep, and insert the sliced garlic pieces into these pockets.

In a small bowl, combine the salt, black pepper, smoked paprika, garlic powder, onion powder, dried oregano, brown sugar, and optional cayenne pepper. Mix thoroughly until well integrated.

Drizzle the olive oil over the entire surface of the meat and massage it in. Apply the dry rub mixture generously to all sides of the tri-tip, pressing gently to help it adhere. For maximum flavor, you can wrap the seasoned meat in plastic wrap and let it marinate in the refrigerator for 3-4 hours, but this is optional if you're short on time.

Set up your grill for two-zone cooking: one side with direct high heat (approximately 450-500°F) and one side with indirect medium heat. For a charcoal grill, pile the coals on one side; for a gas grill, turn one set of burners to high and leave the other side off or on low.

Place the tri-tip on the hot side of the grill, fat side down. Sear for about 4-5 minutes until you have nice grill marks and a good crust has formed. Flip the meat and sear the other side for another 4-5 minutes.

Move the tri-tip to the cooler side of the grill. Close the lid and continue cooking with indirect heat until the internal temperature reaches 130-135°F for medium-rare or 140-145°F for medium, about 20-30 minutes depending on the size of your roast.

Transfer the grilled tri-tip to a cutting board and tent loosely with aluminum foil. Allow it to rest for 15-20 minutes. This critical step allows the juices to redistribute throughout the meat for maximum tenderness.

Note that tri-tip has two different grain directions that meet in the middle. For the most tender slices, identify the grain direction and cut perpendicular to it in thin slices (about ¼-inch thick). When you reach the middle where the grain changes direction, rotate the roast and continue slicing against the grain.