Preheat the oven to 425 degrees F. Lightly grease a large sheet pan or line it with parchment paper.
Boil the baby potatoes in salted water for 8 to 10 minutes until just slightly tender, then drain well.
Place the potatoes, broccoli, onion, and tomatoes on the sheet pan. Drizzle with olive oil and season with half the salt, black pepper, garlic powder, onion powder, and Italian seasoning. Toss gently.
Push the vegetables to the sides and place the steak in the center of the pan. Season the steak with the remaining salt, black pepper, garlic powder, onion powder, and Italian seasoning.
In a small bowl, stir together the melted butter, garlic, parsley, rosemary if using, and lemon juice if using. Spoon half over the steak and vegetables.
Bake for 18 to 22 minutes, until the steak is cooked to your liking and the vegetables are tender and lightly browned.
Let the steak rest for 5 minutes, then slice against the grain. Drizzle with the remaining garlic butter mixture before serving.
Serve hot straight from the pan. Store leftovers in the fridge for up to 3 days.
