Preheat the oven to 350°F (175°C). Spread the cashews on a small baking sheet and toast in the oven until lightly golden, about 10–12 minutes. Remove and set aside.
Cut the chicken breast into bite-sized pieces and season lightly with sea salt and black pepper.
Heat the avocado oil in a large skillet or wok over medium-high heat. Add the chicken and cook until almost done with a small amount of pink remaining, about 4–6 minutes.
Add the chopped red bell pepper, sliced green onions, and minced garlic to the skillet. Cook, stirring, until the vegetables are tender and the chicken is no longer pink, about 3–4 minutes.
Pour in the rice vinegar and cook until it mostly evaporates, about 1–2 minutes.
In a small bowl, whisk together the water, coconut aminos, fresh hot chili paste, honey, and Chinese five-spice powder until smooth.
Pour the sauce mixture into the skillet, increase the heat to high, and bring to a boil. Cook, stirring, until the sauce thickens slightly, about 2–3 minutes.
Remove the skillet from the heat and stir in the sesame oil and toasted cashews.
Serve the cashew chicken over cooked white rice or cauliflower rice, and garnish with additional sliced green onions and sesame seeds.