Cook the brown rice according to package instructions and set aside.
In a small bowl, whisk together the coconut aminos, rice vinegar, tomato paste, and arrowroot powder until smooth to create the sauce.
Cut the chicken breast into bite-sized pieces and season with sea salt and black pepper.
Heat the avocado oil in a large skillet over medium-high heat. Add the chicken and cook until browned and cooked through, then remove from the pan.
In the same skillet, add the sliced bell peppers, onion, minced ginger, and minced garlic. Sauté for 3-4 minutes until the vegetables are tender-crisp.
Return the chicken to the skillet and add the pineapple chunks.
Pour the sauce over the mixture and stir constantly for 1-2 minutes until the sauce thickens and coats everything evenly.
Serve the sweet and sour chicken immediately over the cooked brown rice.