In a large skillet over medium heat, heat ghee. To the skillet, add the chicken, tomatoes,onion and salt, and pepper. Cook for 10 minutes, until chicken, is cooked through. To the chicken, add the spinach and the zucchini noodles. Reduce heat to low and cook zoodles for 5 to 10 minutes, until the spinach wilts and the chicken is cooked through. Serve warm.