Preheat your oven to 400°F (200°C) and line a baking sheet with parchment paper.
Peel the sweet potato and cut it into uniform 1/2-inch cubes.
In a small bowl, toss the sweet potato cubes with half of the olive oil, half of the sea salt, and all of the dried rosemary.
Spread the potatoes on the baking sheet and roast for 20-25 minutes, flipping halfway through, until they are golden and caramelized.
While the potatoes roast, season both sides of the sirloin steak with the remaining sea salt, black pepper, and garlic powder.
Heat a cast-iron skillet over medium-high heat with the remaining olive oil until shimmering.
Place the steak in the hot skillet and sear for 3-4 minutes per side for medium-rare, or until it reaches your desired level of doneness.
Remove the steak from the pan and let it rest on a cutting board for 5 minutes to retain its juices.
While the steak rests, steam the broccoli florets in a steamer basket over boiling water for 4-5 minutes until tender-crisp and vibrant green.
Slice the steak against the grain and serve alongside the roasted sweet potatoes and steamed broccoli.