Preheat oven to 400° F. Season steak with kosher salt and crushed black pepper. Heat cast iron skillet or other oven-safe heavy-duty skillet medium-high heat. Add a smidge of olive oil and swirl around the pan.
Sear steak in cast iron skillet for 4 minutes on top and bottom of steak. Sear sides 30 seconds each. With fat cap side down, place steak in the oven and cook about 20 minutes (10 minutes per pound) or until the thermometer reads 130° F for medium-rare or medium 140°F. Anything more than that and it'll be dry.
Transfer steak onto a cutting board and let rest for 10 minutes. If you want it to continue to cook to reduce redness, tent it with aluminum foil.
Ginger-Soy Vinaigrette
Combine all ingredients into a small bowl or ramekin. Set aside.
Salad
While steak is resting, place all salad ingredients except avocado, peanuts, shaved parmesan (optional) & sesame seeds into a large bowl. Using salad spoon and fork, toss the salad to combine.
Assembly
Once steak is cooled, carefully slice along the grain for a proper cut. Ignoring that is fine too, it just might not look that pretty.
Divide and plate salad onto 4 plates. Top with avocado, peanuts, shaved parmesan (optional), and sesame seeds.
Add a couple pieces of steak onto each plate. Keep any leftover steak for another meal or additional helping.