Dice the chicken breast into bite-sized pieces and season evenly with sea salt and black pepper.
In a small mixing bowl, whisk together the coconut aminos, rice vinegar, tomato paste, minced fresh ginger, and minced garlic to create the sauce.
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, then remove and set aside.
In the same skillet, add the sliced bell peppers and red onion, sautéing for 3-4 minutes until tender-crisp.
Return the chicken to the pan along with the pineapple chunks and the prepared sauce mixture.
Toss everything together and simmer for 2 minutes until the sauce thickens and coats the ingredients.
In a separate pan or microwave, steam the cauliflower rice until tender.
Portion the cauliflower rice into a bowl and top with the sweet and sour chicken mixture.