Preheat your oven to 400°F (200°C) and line a large sheet pan with parchment paper for easy cleanup.
Pat the chicken breast dry with a paper towel to ensure a good sear, then place it on one side of the prepared pan.
Trim the tough, woody ends off the asparagus spears and arrange them in a single layer on the other side of the pan.
In a small bowl, whisk together the olive oil, minced garlic, dried rosemary, dried thyme, sea salt, and black pepper until well combined.
Drizzle the herb oil mixture over both the chicken and the asparagus, using your hands or a brush to coat every surface thoroughly.
Slice the half lemon into thin rounds and place them directly on top of the chicken and tucked among the asparagus spears.
Roast in the center of the oven for 20-25 minutes, or until the chicken reaches an internal temperature of 165°F and the asparagus is lightly charred.
Remove from the oven and let the chicken rest for 5 minutes before slicing to keep the juices locked inside.