Cut the chicken breast into 1-inch cubes and season evenly with sea salt and black pepper.
Heat the avocado oil in a large skillet over medium-high heat until shimmering.
Add the chicken to the skillet and sear until golden brown and cooked through, approximately 6 to 8 minutes.
Remove the chicken from the pan and set aside on a plate.
In the same skillet, add the diced red bell pepper and red onion, sautéing for 4 minutes until they are crisp-tender.
In a small bowl, whisk together the coconut aminos, rice vinegar, honey, and arrowroot powder until smooth.
Add the pineapple chunks and the sauce mixture to the skillet with the vegetables, stirring constantly.
Return the cooked chicken to the skillet and toss everything together for 1 to 2 minutes until the sauce thickens into a glossy glaze.
Serve the glazed chicken and vegetables over the warm brown rice and garnish with sesame seeds.