Preheat your oven to 400°F and line a rimmed baking sheet with parchment paper.
Pat the chicken breast dry with a paper towel to ensure the skin and herbs crisp up beautifully.
In a small bowl, whisk together half of the olive oil, minced garlic, finely chopped rosemary, sea salt, and black pepper.
Rub the herb oil mixture evenly over both sides of the chicken breast and place it in the center of the baking sheet.
Slice the half lemon into thin rounds and arrange them directly on top of the chicken breast.
Roast the chicken in the oven for 10 minutes.
While the chicken is roasting, trim the woody ends off the asparagus and toss the spears with the remaining olive oil.
Remove the baking sheet from the oven, arrange the asparagus around the chicken, and return to the oven for another 12 minutes.
Check that the chicken has reached an internal temperature of 165°F and the asparagus is tender.
Let the chicken rest for 5 minutes before slicing to keep the meat succulent and juicy.