In a small bowl, whisk together the coconut aminos, rice vinegar, tomato puree, minced ginger, and minced garlic to create the sauce.
Cut the chicken breast into bite-sized cubes and season with sea salt and black pepper.
Heat the avocado oil in a large skillet or wok over medium-high heat.
Add the chicken to the skillet and sear until golden brown and cooked through, approximately 5 to 7 minutes.
Remove the chicken from the skillet and set 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.
Add the pineapple chunks to the vegetables and cook for another 2 minutes until the pineapple is warmed through and slightly caramelized.
Return the cooked chicken to the skillet and pour the prepared sauce over the mixture.
Toss everything together for 1 to 2 minutes until the sauce has thickened slightly and evenly coats the chicken and vegetables.
Garnish with sesame seeds and serve immediately while hot.