Remove tri tip from refrigerator, season liberally with spices on all sides and allow to come up in temperature about 10 minutes while you prepare other ingredients.
Heat a large cast iron skillet over medium high heat add olive oil. Place tri tip in skillet and brown on all sides.
Turn heat down to medium and cook tri tip for about 7 minutes on each side, flipping once. When the meat reaches an internal temperature of 125-126ºF add in butter, garlic, shallots and rosemary. With a spoon, spoon the melted butter over the roast as it continues to cook and come up to temperature.
Remove the roast from the pan once it is 5 degrees below your desired doneness, see post above. For this recipe the roast was cooked to 130ºF
Allow the roast to rest before slicing against the grain.
One of my favorite easy rubs to use is this BEEF RUB from Hey Grill Hey.