disingenuously

/ˌdɪsɪnˈdʒɛnjuəsli/
adverb
  1. In a way that is not honest or sincere; pretending to be less knowledgeable or straightforward than one is.
    • The company disingenuously advertised the product as eco-friendly.
    • She smiled disingenuously while hiding her true feelings.
    • He disingenuously claimed he had never seen the email.