Season the Striploin (Pulehu Rub): In a small bowl, combine Hawaiian salt, black pepper, garlic powder, ginger, and onion powder. Rub the striploin lightly with shoyu, liquid smoke and oil, then coat evenly with the pulehu rub. Let rest at room temperature 30–45 minutes before roasting.
Roast the Beef: Preheat oven to 450°F (230°C). Place roast on a rack in a roasting pan. Roast for 15 minutes to develop a crust. Lower oven to 325°F (165°C) and continue roasting until internal temperature reaches 120°F rare, 130°F medium-rare, 140°F medium. Remove, tent with foil, and rest 20–30 minutes.
Make the Horseradish Sauce: Stir together sour cream, horseradish, chili pepper water, green onion, and salt. Chill until ready to serve.
Prepare Lomi Tomato: Combine diced tomatoes, onion, Hawaiian salt, and green onion. Mix gently, adding ice cubes if desired. Chill until serving.
Serve Family-Style: Place the whole rested striploin on a cutting board or platter. Carve to order in thin slices. Serve with bowls of horseradish sauce and lomi tomato on the side. Guests can build their own sliders with warm Hawaiian rolls.