Preheat your oven to 400°F (200°C) and line a small baking sheet with parchment paper.
Dice the Yukon Gold potatoes into half-inch cubes and place them in a bowl.
Toss the potatoes with 0.25 tablespoons of olive oil, the dried rosemary, and half of the sea salt and black pepper.
Spread the potatoes evenly on the baking sheet and roast for 20 to 25 minutes until golden and crispy on the edges.
While the potatoes roast, pat the sirloin steak dry with a paper towel and season both sides with the remaining salt and pepper.
Heat a cast-iron skillet over medium-high heat with the remaining 0.25 tablespoons of olive oil.
Once the skillet is shimmering, sear the steak for 3 to 4 minutes per side for medium-rare, adding the minced garlic to the pan during the final minute of cooking.
Remove the steak from the pan and let it rest on a cutting board for at least 5 minutes to lock in the juices.
While the steak rests, steam or lightly sauté the asparagus spears until they are tender-crisp and bright green.
Slice the steak against the grain and serve immediately alongside the roasted potatoes and steamed asparagus.