Preheat your oven to 400°F (200°C) and line a large baking sheet with parchment paper.
Peel and cube the sweet potato into 1/2-inch pieces, then toss them on the baking sheet with avocado oil, dried thyme, and half of the sea salt.
Roast the sweet potatoes for 15 minutes, then move them to one side of the tray and add the trimmed asparagus spears to the other side.
Season the asparagus with a pinch of salt and pepper, then roast everything for an additional 10-12 minutes until the potatoes are golden and asparagus is tender.
While the vegetables finish roasting, season the sirloin steak generously on both sides with the remaining salt and pepper.
Heat a cast-iron skillet over medium-high heat. Once hot, sear the steak for 3-4 minutes per side to reach your desired level of doneness.
In the final minute of cooking, add the ghee and minced garlic to the skillet. Once melted, tilt the pan and spoon the garlic butter over the steak repeatedly.
Transfer the steak to a cutting board and let it rest for 5 minutes before slicing against the grain and serving alongside the roasted vegetables.