Preheat your oven to 400°F (200°C).
Peel the sweet potato and cut it into 1/2-inch cubes.
On a large baking sheet, toss the sweet potato cubes with half of the olive oil and a pinch of sea salt and black pepper.
Roast the sweet potatoes for 15 minutes.
While potatoes roast, trim the woody ends off the asparagus; add them to the baking sheet after the initial 15 minutes and roast for another 10 minutes.
Season the steak generously on both sides with the remaining sea salt and black pepper.
Heat a cast-iron skillet over medium-high heat with the remaining olive oil.
Once the pan is shimmering, sear the steak for 2-3 minutes per side to develop a deep golden crust.
Add the smashed garlic clove and the rosemary sprig to the pan, then transfer the skillet directly into the oven.
Roast the steak for 4-6 minutes, or until it reaches your preferred level of doneness.
Remove the steak from the oven and let it rest on a cutting board for 5 minutes before slicing against the grain.
Serve the sliced steak alongside the roasted sweet potatoes and asparagus.