Dice the chicken breast into bite-sized cubes and season evenly with sea salt and black pepper.
In a small mixing bowl, whisk together the coconut aminos, rice vinegar, tomato paste, arrowroot powder, minced garlic, and grated fresh ginger to create the sauce.
Heat the sesame oil in a large skillet or wok over medium-high heat.
Add the chicken to the skillet and sauté until golden brown and cooked through, approximately 5 to 7 minutes.
Remove the cooked chicken from the skillet and set it aside on a plate.
In the same skillet, add the chopped bell pepper, red onion, and snap peas, sautéing for 3 to 4 minutes until they are tender-crisp.
Stir in the fresh pineapple chunks and the prepared sauce mixture, simmering for 1 to 2 minutes until the glaze thickens and bubbles.
Return the chicken to the skillet and toss everything together to ensure the chicken and vegetables are thoroughly coated in the sauce.
Serve the sweet and sour chicken immediately over the warm cooked brown rice.