Prepare the sauce by whisking coconut aminos, rice vinegar, honey, tomato paste, minced ginger, and minced garlic in a small bowl until smooth.
Season the diced chicken breast evenly with sea salt and black pepper.
Heat the sesame oil in a large skillet or wok over medium-high heat until shimmering.
Add the chicken to the skillet and sear until golden brown and cooked through, approximately 5 to 7 minutes.
Remove the cooked chicken from the pan and set it aside on a plate.
In the same skillet, add the diced bell peppers and red onion, sautéing for 3 to 4 minutes until they are tender yet still crisp.
Stir in the pineapple chunks and the prepared sauce, allowing the mixture to simmer for 2 minutes until the glaze thickens slightly.
Return the chicken to the pan and toss thoroughly to coat every piece in the glossy sweet and sour glaze.
Serve the stir-fry immediately over a portion of warm cooked brown rice.