Remove the tri-tip from the refrigerator about 45 minutes before cooking to bring it to room temperature. Using a sharp knife, make small slits all over the surface of the meat and insert the sliced garlic pieces into these slits.

In a small bowl, combine salt, pepper, garlic powder, onion powder, dried oregano, dried rosemary, smoked paprika, and cayenne pepper (if using). Drizzle the tri-tip with olive oil, then massage the dry rub mixture all over the meat, ensuring complete coverage. Let it sit for at least 30 minutes.

Prepare your grill for two-zone cooking with direct and indirect heat zones. For a gas grill, preheat to 450-500°F on one side. For a charcoal grill, arrange coals on one side.

Place the tri-tip on the direct heat zone and sear each side for about 4-5 minutes until you achieve a nice caramelized crust.

After searing, move the tri-tip to the indirect heat zone. Close the grill lid. Cook for 15-20 minutes for rare (125-130°F), 20-25 minutes for medium-rare (130-135°F), or 25-30 minutes for medium (135-145°F).

Once the tri-tip reaches your desired internal temperature, remove it from the grill and place it on a cutting board. Tent loosely with aluminum foil and let it rest for 10-15 minutes.

Slice the meat into thin slices (about 1/4 inch thick) perpendicular to the grain for maximum tenderness.