In a small bowl, whisk together the coconut aminos, apple cider vinegar, honey, tomato paste, arrowroot powder, garlic powder, and ginger powder until smooth.
Cut the chicken breast into bite-sized cubes and season evenly with sea salt and black pepper.
Heat the toasted sesame oil in a large non-stick skillet or wok over medium-high heat.
Add the chicken to the skillet and cook, stirring occasionally, until golden brown and cooked through, about 6 to 8 minutes.
Remove the chicken from the skillet and set aside on a plate.
In the same skillet, add the diced red bell pepper, red onion, and pineapple chunks.
Sauté for 3 to 4 minutes until the vegetables are tender-crisp and the pineapple begins to caramelize at the edges.
Return the cooked chicken to the skillet and pour the prepared sauce over the mixture.
Stir constantly for 1 to 2 minutes until the sauce thickens and creates a glossy glaze over the chicken and vegetables.
Serve the sweet and sour chicken immediately over the warm cooked brown rice.