Preheat oven with rack in the middle, to 425 degrees.

Place tri tip on a cutting board or work surface.  Sprinkle generously with kosher salt and black pepper, or steak seasoning, if using.

Heat a large, oven proof skillet (cast iron is an excellent choice) to medium heat on the stove top.  When hot add about 1 tablespoon of olive oil and swirl to coat bottom of pan.

Add roast and sear each side for 2-3 minutes, until a deep golden brown crust forms.

Transfer skillet to oven and cook until an instant-read digital thermometer inserted in the thickest portion reaches temperature (see guide below).  Usually about 10-12 minutes per pound. I pull mine between 138°- 140°

While roast is cooking, make sure to have your butter ready, as well as garlic and herbs if using.

Remove roast and immediately add 4 tablespoons butter (and minced garlic, if using) to hot skillet.  Mix it around a little to melt and let the garlic cook. 

Using a potholder or towel (remember that skillet is HOT) tilt the pan and use a spoon to spoon the garlic-butter-pan juices over the top of the roast a few times. **Alternately- you can remove your pan from the oven and place on stove top and immediately remove roast from pan and set on a cutting board and tent with foil.  Then place your butter/garlic/herbs into the pan on the stove top and cook.  At this point with your roast removed, you can turn your pan on low heat if needed, without overcooking your meat.  I sometimes do this if I've let my roast cook a little longer than I had planned, or if my pan doesn't seem hot enough to be cooking my garlic. Then simply return sliced meat back to warm pan, or spoon buttery juices over sliced meat.

Tent Skillet with foil and let sit for 10 minutes before serving.

To serve, place steak on a cutting board and slice against the grain (see photo guide in article, and note that meat grain changes direction in this cut of roast).  I like thin slices, about 1/4 inch, but slice however thick or thin you like!

Use a wooden spoon or heat-proof rubber spatula to stir butter and juices in pan and then spoon over sliced meat.  Alternately you can place the sliced meat back into the pan with juices to serve (this is what I usually do!)