Preheat your oven to 400°F (200°C) and line a large baking sheet with parchment paper for easy cleanup.
Mince the garlic clove and finely chop the fresh rosemary leaves.
Zest the entire lemon into a small bowl, then cut it in half and squeeze the juice into the same bowl.
Whisk the extra virgin olive oil, lemon juice, lemon zest, minced garlic, and chopped rosemary together until well combined.
Place the chicken breast on one side of the prepared baking sheet and season both sides with the sea salt and black pepper.
Trim the woody ends off the asparagus spears and arrange them in a single layer on the other side of the baking sheet.
Drizzle the lemon-herb oil mixture over both the chicken and the asparagus, tossing the spears to ensure they are evenly coated.
Roast in the center of the oven for 20 to 25 minutes, or until the chicken reaches an internal temperature of 165°F and the asparagus is tender.
Let the chicken rest for 5 minutes before slicing to keep it juicy, then serve immediately alongside the roasted asparagus.