Cut the chicken breast into bite-sized pieces and season with sea salt and black pepper.
In a small bowl, whisk together the coconut aminos, apple cider vinegar, tomato paste, minced ginger, minced garlic, and arrowroot powder until smooth.
Heat the sesame oil in a large skillet over medium-high heat.
Add the chicken to the skillet and sauté until golden brown and cooked through, about 6 minutes.
Remove the chicken from the skillet and set aside.
Add the diced red bell pepper, green bell pepper, and red onion to the same skillet, cooking for 3-4 minutes until tender-crisp.
Stir in the fresh pineapple chunks and cook for 1 minute more.
Return the chicken to the skillet and pour in the whisked sauce mixture.
Toss everything together constantly for 1-2 minutes until the sauce is thick, glossy, and coats the chicken and vegetables.
Serve the sweet and sour chicken immediately over the steamed cauliflower rice.