Pat the chicken breast dry with a paper towel and cut into bite-sized pieces.
In a small bowl, toss the chicken with arrowroot powder, sea salt, and black pepper until evenly coated.
Heat avocado oil in a large skillet or wok over medium-high heat.
Add the chicken to the pan and sear for 5-6 minutes, turning occasionally until golden brown and cooked through, then remove chicken and set aside.
In the same pan, add the broccoli florets and sliced red bell pepper, stir-frying for 3-4 minutes until they are bright and crisp-tender.
While the vegetables cook, whisk together the tamari, orange juice, orange zest, minced ginger, and minced garlic in a small jar.
Return the chicken to the pan and pour the orange sauce over the mixture.
Toss everything together for 1-2 minutes until the sauce thickens and becomes glossy.
Remove from heat, drizzle with toasted sesame oil, and serve over the warm brown rice garnished with sliced green onions.