Heat the avocado oil in a large skillet or wok over medium-high heat until shimmering.
Season the cubed chicken breast with sea salt, black pepper, garlic powder, and ground ginger.
Add the chicken to the skillet and sear until golden brown and cooked through, approximately 5 to 7 minutes, then remove and set aside.
In the same skillet, add the chopped red and green bell peppers, red onion, and pineapple chunks, sautéing for 3 to 4 minutes until the vegetables are tender-crisp.
While the vegetables cook, whisk together the coconut aminos, rice vinegar, honey, and tomato paste in a small bowl to create the sauce.
Return the cooked chicken to the skillet and pour the sauce over the chicken and vegetable mixture.
Toss everything together for 1 to 2 minutes until the sauce has thickened and evenly coated all ingredients.
Serve the stir-fry immediately over the warm, cooked brown rice.