In a large frying pan or wok, heat 2 tablespoons of the avocado oil over a medium flame, but not smoking.
Add chicken and cook, stirring continuously until the chicken is tender, about five minutes. Remove the chicken to a plate and set aside. Drain the pan juices from the wok. Wipe the wok clean so it will be ready for cooking your vegetables
Heat the remaining 2 tablespoons of oil. Add spinach and season with turmeric, cumin, and coriander. Cook for 1 minute. Add mushrooms, tomatoes, and onions. Stir and cook for 15 minutes.
Add garam masala and salt. Stir and continue cooking for another minute.
Stir in lemon juice, cilantro, and cayenne pepper (optional).
Toss the chicken back in. Stir until well combined and serve.