Preheat your oven to 400°F and line a baking sheet with parchment paper.
Trim the woody ends off the asparagus, toss with olive oil and a pinch of salt, then roast for 10-12 minutes until tender.
Pat the flank steak dry with paper towels and season both sides generously with sea salt and black pepper.
Heat a heavy cast-iron skillet over medium-high heat until it is starting to smoke slightly.
Place the steak in the hot skillet and sear for 4-5 minutes without moving it to develop a deep brown crust.
Flip the steak and cook for another 3-4 minutes for medium-rare doneness.
In the final 2 minutes of cooking, add the ghee, smashed garlic cloves, and rosemary to the pan.
Tilt the skillet slightly and use a large spoon to continuously baste the steak with the melting garlic-herb ghee.
Transfer the steak to a cutting board and let it rest for at least 5 minutes to lock in the juices.
Slice the steak thinly against the grain and serve immediately with the roasted asparagus.