Preheat your oven to 400°F (200°C) and line a baking sheet with parchment paper.
Trim the woody ends off the asparagus spears and place them on the prepared baking sheet.
Drizzle 0.5 tablespoon of olive oil over the asparagus and toss with half of the sea salt and black pepper.
Roast the asparagus for 12 to 15 minutes until tender and slightly charred at the tips.
While the asparagus roasts, pat the sirloin steak dry with paper towels and season both sides with the remaining salt and pepper.
Heat the remaining 0.5 tablespoon of olive oil in a cast-iron skillet over medium-high heat until shimmering.
Place the steak in the hot skillet and sear for 4 to 5 minutes per side for medium-rare, or until it reaches your desired doneness.
Add the minced garlic to the pan during the last minute of searing, tossing it in the pan juices to prevent burning.
Remove the steak from the skillet and let it rest on a cutting board for 5 minutes before slicing against the grain.
Arrange the sliced steak and roasted asparagus on a plate, then drizzle with fresh lemon juice before serving.