Prep everything first. Thinly slice the chicken and vegetables so they cook quickly.
Stir fry moves fast, and having everything ready makes it smoother.
Season the chicken. In a bowl, toss the chicken with a pinch of salt, black pepper, and 1 teaspoon of tamari or coconut aminos. This adds quick flavor and helps it brown.
Heat the pan hot. Set a large skillet or wok over medium-high heat. Add 1 tablespoon of oil and swirl to coat.
Sear the chicken. Add the chicken in a single layer.
Cook undisturbed for 2–3 minutes to get a little color, then stir and cook another 2–3 minutes until just cooked through. Transfer to a plate.
Sauté aromatics. Add the remaining 1 tablespoon of oil to the pan. Add onion and the white parts of the green onions.
Cook 1–2 minutes until they start to soften. Stir in garlic and ginger, and cook 30 seconds until fragrant.
Cook the veggies. Add the cabbage and bell pepper. Season with a pinch of salt and black pepper.
Stir fry for 3–5 minutes until the cabbage is tender-crisp, not mushy. If the pan looks dry, add a splash of water to create a little steam.
Make it saucy. Return the chicken to the pan. Add the remaining tamari or coconut aminos, rice vinegar, sesame oil, and red pepper flakes or sriracha if using.
Toss everything together until coated and heated through, about 1–2 minutes.
Finish and serve. Turn off the heat. Stir in the green onion tops. Taste and adjust salt, pepper, or vinegar.
Sprinkle sesame seeds on top and serve with lime wedges if you like a fresh pop of acid.