Preheat your oven to 400°F and line a large baking sheet with parchment paper.
Peel and cube the sweet potato into 1-inch pieces, then toss on the baking sheet with olive oil and half of the sea salt.
Roast the sweet potatoes for 20-25 minutes, tossing halfway through, until they are tender and slightly caramelized.
While potatoes roast, steam the broccoli florets in a steamer basket over boiling water for 5-6 minutes until bright green and crisp-tender.
Pat the sirloin steak dry with paper towels and season both sides generously with the remaining sea salt and black pepper.
Heat a cast-iron skillet over medium-high heat; once hot, sear the steak for 3-4 minutes per side for medium-rare.
Reduce heat to medium and add the ghee, smashed garlic cloves, and fresh rosemary to the pan.
Tilt the pan and use a spoon to continuously baste the steak with the melted herb ghee for 1 minute.
Remove the steak from the pan and let it rest on a cutting board for 5 minutes before slicing against the grain.
Plate the sliced steak alongside the roasted sweet potatoes and steamed broccoli, drizzling any remaining pan juices over the meat.