In a small bowl, whisk together the pineapple juice, coconut aminos, tomato paste, and apple cider vinegar until smooth.
Season the diced chicken breast with sea salt and black pepper.
Heat avocado oil in a large skillet over medium-high heat and sear the chicken until golden brown and cooked through, then remove from the pan.
In the same skillet, add the sliced bell peppers and red onion, sautéing until they are tender yet crisp.
Stir in the minced garlic and fresh ginger, cooking for 1 minute until fragrant.
Return the chicken to the skillet along with the pineapple chunks and the prepared sauce, tossing everything to coat well.
Simmer for 2-3 minutes until the sauce has thickened into a glossy glaze.
In a separate pan or microwave, lightly steam the cauliflower rice until tender.
Drizzle the stir-fry with sesame oil and serve immediately over the cauliflower rice.