Preheat your oven to 400°F (200°C) and line a large baking sheet with parchment paper.
Cut the chicken breast into 1-inch bite-sized pieces and place them in a bowl, seasoning with sea salt and black pepper.
In a separate small jar or bowl, whisk together the orange juice, orange zest, tamari, rice vinegar, honey, arrowroot powder, minced garlic, and grated ginger.
Spread the chicken and broccoli florets across the prepared baking sheet in a single layer.
Drizzle the sesame oil over the chicken and broccoli, then pour half of the orange sauce mixture over the top, tossing well to coat everything evenly.
Bake for 15 to 18 minutes, or until the chicken is cooked through and the broccoli is tender with slightly crispy edges.
While the chicken bakes, pour the remaining orange sauce into a small saucepan and simmer over medium heat for 3 minutes until it thickens into a glossy glaze.
Serve the baked orange chicken and broccoli over the warm cooked brown rice, drizzled with the extra glaze and garnished with fresh green onions.