Preheat your oven to 400°F (200°C) and line a baking sheet with parchment paper.
Trim the woody ends off the asparagus and place the spears on the baking sheet.
Mince the garlic and toss the asparagus with half of the avocado oil, the minced garlic, and a pinch of salt and pepper.
Roast the asparagus for 12 to 15 minutes until tender and slightly charred at the tips.
While the vegetables roast, pat the sirloin steak completely dry with a paper towel and season both sides with the remaining salt, pepper, and finely chopped rosemary.
Heat the remaining avocado oil in a heavy cast-iron skillet over medium-high heat until shimmering.
Place the steak in the hot skillet and sear for 3 to 4 minutes per side for medium-rare, or until it reaches your desired doneness.
Remove the steak from the pan and let it rest on a cutting board for at least 5 minutes to allow the juices to redistribute.
Slice the steak against the grain and serve alongside the roasted garlic asparagus.