Preheat your oven to 400°F (200°C) and line a small baking sheet with parchment paper.
Trim the woody ends off the asparagus, toss with olive oil and a pinch of the salt and pepper, then roast for 10-12 minutes until tender.
While the asparagus roasts, pat the sirloin steak completely dry with paper towels to ensure a proper sear.
Season both sides of the steak generously with the remaining sea salt and black pepper.
Heat a heavy cast-iron skillet over medium-high heat until it begins to smoke slightly.
Place the steak in the hot skillet and sear for 3-4 minutes per side without moving it, creating a deep golden-brown crust.
Reduce the heat to medium and add the ghee, smashed garlic cloves, and the rosemary sprig to the pan.
Tilt the skillet slightly and use a large spoon to continuously pour the hot, bubbling garlic ghee over the steak for 2 minutes.
Remove the steak from the pan and let it rest on a cutting board for 5 minutes to allow the juices to redistribute.
Slice the steak against the grain and serve alongside the roasted asparagus, drizzling any remaining pan juices over the top.