Step 1 Combine lemon juice, sugar, soy sauce, sesame oil, cornflour and pepper in a jug. Set aside until needed. Soak noodles in warm water as per packet instructions, until tender. Drain.
Step 2 Slice chicken breast fillets into thin strips. Place a wok over high heat. Once wok is hot, spray with oil. Add 1/4 of the chicken and stir-fry for 2 minutes, or until browned. Transfer chicken to a plate. Cook remaining chicken in batches, spraying with more oil if required.
Step 3 Reheat wok and spray with oil. Add onions, beans, snow peas and capsicum. Stir-fry for 1 minute. Add 1 tablespoon water, then cover and cook for 1 minute, or until vegetables are tender-crisp. Return chicken to wok with noodles and lemon dressing. Toss for 2 minutes, until hot and dressing is slightly thickened. Top with basil leaves and lemon zest to serve.