In a small bowl, whisk together the tamari, rice vinegar, honey, tomato paste, red pepper flakes, arrowroot powder, and water until smooth to create the sauce.
Cut the chicken breast into bite-sized pieces and season lightly with a pinch of salt if desired.
Heat the avocado oil in a large skillet or wok over medium-high heat.
Add the chicken to the skillet and sear for 5-6 minutes, stirring occasionally, until browned and cooked through.
Add the broccoli florets, sliced red bell pepper, minced garlic, and grated ginger to the skillet, sautéing for 3-4 minutes until the vegetables are tender-crisp.
Pour the prepared sauce over the chicken and vegetables, tossing constantly for 1-2 minutes until the sauce thickens and glazes the ingredients.
Serve the stir-fry immediately over the warm cooked brown rice and garnish with sesame seeds.