Preheat your oven to 400°F (200°C) and line a large rimmed baking sheet with parchment paper.
Rinse the quinoa in a fine-mesh sieve under cold water, then place it in a small saucepan with 0.5 cup of water and a pinch of salt.
Bring the quinoa to a boil, then reduce heat to low, cover, and simmer for 15 minutes until the water is absorbed; let it sit covered for 5 minutes before fluffing with a fork.
In a small bowl, whisk together the minced garlic, lemon zest, dried rosemary, dried thyme, and half of the olive oil to create a herb paste.
Pat the chicken breast dry with paper towels and rub the herb paste evenly over all sides before placing it on one side of the prepared baking sheet.
Toss the broccoli florets with the remaining olive oil, sea salt, and black pepper on the other side of the baking sheet, spreading them into a single layer.
Roast for 20 to 25 minutes, or until the chicken reaches an internal temperature of 165°F and the broccoli is tender with crispy, charred edges.
Slice the chicken and serve it over the fluffy quinoa with the roasted broccoli, finishing the dish with a fresh squeeze of lemon juice over everything.