Preheat your oven to 400°F (200°C) to roast the vegetables.
Trim the woody ends off the asparagus, place them on a baking sheet, toss with the olive oil, and season with half of the sea salt and black pepper.
Roast the asparagus for 10-12 minutes until tender-crisp and slightly charred.
While the asparagus roasts, pat the sirloin steak completely dry with paper towels and season both sides with the remaining salt and pepper.
Heat a cast-iron skillet over medium-high heat until very hot, then sear the steak for 3-4 minutes per side for a medium-rare finish.
Reduce the heat to medium-low and add the grass-fed butter, smashed garlic cloves, rosemary, and thyme to the skillet.
Tilt the pan slightly and use a large spoon to continuously baste the steak with the melted herb butter for about 2 minutes.
Transfer the steak to a cutting board and let it rest for 5 minutes to allow the juices to redistribute.
Slice the steak against the grain and serve immediately alongside the roasted asparagus, drizzling any remaining pan butter over the top.