Cut the chicken breast into bite-sized cubes and season with sea salt, black pepper, garlic powder, and ground ginger.
In a small bowl, whisk together the tomato puree, coconut aminos, rice vinegar, and honey to create the sweet and sour sauce base.
Heat the sesame oil in a large skillet over medium-high heat until shimmering.
Add the chicken to the skillet and sauté until golden brown and cooked through, approximately 5-7 minutes.
Remove the chicken from the pan and set aside on a plate.
Add the diced red bell pepper, red onion, and pineapple chunks to the same skillet, sautéing for 3-4 minutes until the vegetables are tender-crisp.
Return the chicken to the pan and pour the prepared sauce over the mixture.
Stir constantly for 1-2 minutes until the sauce thickens and coats the chicken and vegetables evenly.
Serve the sweet and sour chicken immediately over the warm cooked brown rice.