In a small bowl, whisk together the coconut aminos, rice vinegar, honey, tomato paste, minced ginger, and minced garlic to create the sweet and sour sauce.
Cut the chicken breast into 1-inch bite-sized cubes and season evenly with sea salt and black pepper.
Heat the avocado oil in a large skillet or wok over medium-high heat until shimmering.
Add the chicken to the skillet and sauté for 5-6 minutes, turning occasionally, until golden brown and cooked through.
Add the sliced red bell pepper, snap peas, and pineapple chunks to the skillet, stir-frying for an additional 3-4 minutes until the vegetables are tender-crisp.
Pour the prepared sauce over the chicken and vegetables, tossing constantly for 1-2 minutes until the sauce thickens and coats everything beautifully.
Serve the stir-fry immediately over the warm cooked brown rice and garnish with sesame seeds.