In a mixing bowl, combine the cubed flank steak or tenderloin, black pepper, arrowroot or cornstarch, 1 tablespoon of sesame or olive oil, Gochujang, and tamari or soy sauce. Mix well until the beef is evenly coated. Let it marinate for about 15-30 minutes for maximum flavor.
Preheat your oven to 425°F (220°C). This high temperature will help achieve that desirable caramelization on the beef and veggies.
On a large sheet pan, spread the marinated beef in an even layer. Add the sliced zucchini, red bell peppers, and patted dry pickled ginger around the beef.
Melt the salted butter and mix in the chopped garlic. Drizzle this mixture over the beef and vegetables, ensuring everything is well-coated.
Roast the sheet pan in the preheated oven for about 20-25 minutes, or until the beef is cooked to your liking and the vegetables are tender. Don’t forget to toss everything halfway through for even cooking.
While the beef and veggies are roasting, cook your rice according to package instructions. Fluff it up and set aside.
Once everything is cooked, it’s time to assemble your bowls! Start with a scoop of rice, then top with the beef and roasted vegetables. Drizzle with mayo mixed with ginger juice, sprinkle with chili flakes, and finish off with sesame seeds.