Preheat your oven to 425°F (220°C).
Halve the fingerling potatoes and toss them on a baking sheet with 0.25 tablespoons of olive oil, a pinch of sea salt, and black pepper.
Roast the potatoes for 15 minutes, then add the trimmed asparagus to the same tray, tossing to coat in the residual oil, and roast for an additional 8-10 minutes until tender.
While vegetables roast, pat the sirloin steak dry with paper towels and season both sides with the remaining sea salt and black pepper.
Heat a heavy cast-iron skillet over medium-high heat. Once hot, sear the steak for 3-4 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 lock in the juices.
In a small bowl, whisk together the remaining 0.5 tablespoons of olive oil, minced garlic, chopped parsley, minced rosemary, minced thyme, and lemon zest to create the herb oil.
Slice the steak against the grain and arrange on a plate with the roasted potatoes and asparagus, drizzling the fresh herb oil over the beef just before serving.