Pat the chicken breast dry with a paper towel and toss in a bowl with arrowroot powder, sea salt, and black pepper until evenly coated.
Heat the avocado oil in a large skillet over medium-high heat until shimmering.
Add the chicken to the skillet and sear for 5-6 minutes, turning occasionally, until the edges are golden and crispy.
Remove the chicken from the pan and set aside; add the red bell pepper, snap peas, and pineapple chunks to the same skillet.
Sauté the vegetables for 3-4 minutes until they are tender-crisp and the pineapple starts to caramelize.
In a small jar, whisk together the coconut aminos, rice vinegar, honey, and sesame oil.
Return the chicken to the skillet, pour the sauce over the mixture, and stir for 1 minute until the glaze is thick and glossy.
Serve the stir-fry over the warm brown rice and garnish with sesame seeds.