Preheat your oven to 400°F (200°C) and trim the woody ends off the asparagus.
Pat the chicken thighs completely dry with a paper towel to ensure the skin gets maximum crispiness.
In a small bowl, combine the sea salt, black pepper, dried rosemary, and garlic powder.
Season the chicken thighs generously on both sides with half of the spice mixture.
Heat the olive oil in a large oven-safe skillet over medium-high heat.
Place the chicken skin-side down in the hot skillet and sear for 6 minutes until the skin is golden and crackling.
Flip the chicken, then toss the asparagus into the pan around the chicken, seasoning the spears with the remaining spices.
Transfer the skillet to the oven and roast for 12-15 minutes until the chicken reaches an internal temperature of 165°F.
Finish the dish with a bright squeeze of fresh lemon juice over the chicken and asparagus before serving.