Preheat your oven to 400°F and line a baking sheet with parchment paper.
Peel and cube the sweet potato into 1/2-inch pieces, then trim the woody ends off the asparagus.
Toss the sweet potato and asparagus with a small drizzle of avocado oil and a pinch of salt; roast for 20 minutes until the potatoes are tender and the asparagus is crisp-tender.
While the vegetables roast, pat the sirloin steak dry with paper towels and season both sides with sea salt and black pepper.
Heat a cast-iron skillet over medium-high heat with the remaining avocado oil until the pan is shimmering and just starting to smoke.
Carefully place the steak in the skillet and sear for 3-4 minutes per side to develop a deep golden-brown crust.
Reduce the heat to medium-low and add the ghee, minced garlic, rosemary, and thyme to the pan.
Tilt the skillet slightly and use a spoon to continuously baste the steak with the melting herb ghee for about 60 seconds.
Transfer the steak to a cutting board and let it rest for at least 5 minutes to allow the juices to redistribute.
Slice the steak against the grain and serve alongside the roasted sweet potatoes and asparagus.