Cut the chicken breast into bite-sized 1-inch cubes and place them in a small bowl.
Toss the chicken with arrowroot powder, sea salt, and black pepper until each piece is evenly coated.
In a small jar or bowl, whisk together the coconut aminos, rice vinegar, tomato paste, and honey to create the sweet and sour sauce.
Heat the avocado oil in a large non-stick skillet or wok over medium-high heat.
Add the chicken to the skillet in a single layer and cook for 5-6 minutes, turning occasionally, until the exterior is golden and crispy.
Remove the chicken from the pan and set aside on a plate.
In the same skillet, add the bell peppers and broccoli, stir-frying for 3-4 minutes until tender-crisp.
Add the pineapple chunks and the prepared sauce to the skillet, stirring constantly as the sauce begins to bubble and thicken.
Return the crispy chicken to the pan and toss well to coat every piece in the glossy glaze.
Serve the chicken and vegetables over the warm cooked brown rice and garnish with sesame seeds.