Whisk together the lemon juice, minced garlic, and one teaspoon of olive oil in a small bowl.
Place the chicken breast in a shallow dish or bag, coat with the marinade, and let sit for at least 15 minutes.
Preheat your oven to 400°F and prepare a baking sheet with parchment paper.
Toss the broccoli florets with the remaining teaspoon of olive oil and a pinch of sea salt, then spread them in a single layer on the baking sheet.
Roast the broccoli for 15-20 minutes until the edges are slightly charred and tender.
While the broccoli roasts, heat a grill pan or outdoor grill over medium-high heat.
Grill the chicken for 5-7 minutes per side, or until the internal temperature reaches 165°F.
Let the chicken rest for 5 minutes before slicing.
Serve the sliced chicken alongside the fluffed quinoa and roasted broccoli.