Whisk together the lemon juice, half of the olive oil, and garlic powder in a small bowl to create a marinade.
Place the chicken breast in a shallow dish, coat thoroughly with the marinade, and let it rest for at least 10 minutes.
Preheat your oven to 400°F and line a baking sheet with parchment paper.
Toss the broccoli florets with the remaining olive oil and a pinch of sea salt, then spread them evenly on the baking sheet.
Roast the broccoli for 15-20 minutes until the edges are tender and slightly crispy.
While the broccoli roasts, heat a grill pan or outdoor grill over medium-high heat.
Grill the chicken breast for 6-7 minutes per side or until the internal temperature reaches 165°F.
Warm the pre-cooked quinoa and fluff it with a fork.
Slice the grilled chicken into strips and serve alongside the roasted broccoli and quinoa for a balanced, high-protein lunch.