Start by removing any excess fat from the 2 lb tri-tip. Pat the steak dry with paper towels.
Rub the steak all over with the 1 tbsp olive oil, then sprinkle the 3 tbsp steak rub generously over the surface.
Preheat your cast iron skillet over medium-high heat until very hot.
Carefully place the seasoned tri-tip into the hot skillet. Sear for about 4-5 minutes on one side.
Flip the steak and sear the other side for another 4-5 minutes. Check internal temperature with a meat thermometer.
Transfer the steak to a cutting board and cover loosely with aluminum foil. Let it rest for at least 10 minutes.
After resting, slice the steak against the grain into thin strips and serve.
