Dice the chicken breast into 1-inch cubes and season evenly with sea salt and black pepper.
In a small glass bowl, whisk together the tomato paste, coconut aminos, apple cider vinegar, honey, minced ginger, and minced garlic until smooth.
Heat the avocado oil in a large stainless steel skillet or wok over medium-high heat until shimmering.
Add the chicken cubes to the skillet and sear for 5-6 minutes, turning occasionally, until golden brown and cooked through; remove chicken and set aside.
In the same skillet, add the diced bell peppers, red onion, and pineapple chunks, sautéing for 4 minutes until the vegetables are tender-crisp and the pineapple edges begin to caramelize.
Return the cooked chicken to the skillet and pour the prepared sauce over the mixture.
Toss everything together for 1-2 minutes until the sauce thickens into a glossy glaze that coats every piece.
In a separate small pan, lightly steam or sauté the cauliflower rice with a splash of water for 3 minutes until tender.
Plate the cauliflower rice and top with the sweet and sour chicken mixture, serving immediately while hot.