Pat the chicken breast dry with a paper towel and cut into bite-sized pieces.
In a medium bowl, toss the chicken with arrowroot powder, sea salt, and black pepper until evenly coated.
Heat avocado oil in a large skillet or wok over medium-high heat until shimmering.
Add the chicken to the pan in a single layer and sear until golden brown and crispy on all sides, then remove and set aside.
Add the sliced bell peppers, broccoli florets, and red onion to the same pan, sautéing for 3-4 minutes until tender-crisp.
In a small jar, whisk together the coconut aminos, rice vinegar, tomato paste, and honey to create the sauce.
Return the chicken to the skillet and pour the sauce over the meat and vegetables.
Stir-fry for 1-2 minutes until the sauce thickens into a glossy glaze that coats every piece.
Steam the cauliflower rice and combine it with the warm brown rice in a serving bowl.
Top the rice mixture with the crispy sweet and sour chicken and serve immediately.