Preheat your oven to 400°F (200°C).
Rinse the quinoa under cold water, then combine with 0.5 cup water in a small saucepan; bring to a boil, reduce to low, and simmer covered for 15 minutes.
Trim the woody ends off the asparagus and place the spears on a baking sheet. Toss with 0.5 tbsp of olive oil, a pinch of sea salt, and black pepper.
Roast the asparagus in the oven for 12-15 minutes until tender and slightly charred.
While the asparagus roasts, season the chicken breast with the remaining salt, pepper, and chopped fresh rosemary.
Heat the remaining 0.5 tbsp of olive oil in a skillet over medium-high heat. Sear the chicken for 6-7 minutes per side until the internal temperature reaches 165°F.
During the last 2 minutes of cooking, add the minced garlic and the juice of the half lemon to the skillet, spooning the juices over the chicken to glaze.
Fluff the cooked quinoa with a fork and serve alongside the lemon-herb chicken and roasted asparagus.