form.html

<form id="form" accept-charset="UTF-8" action="https://yourserverlessurl.com" method="POST">
  <input type="hidden" name="redirectUrl" value="https://yourredirect.com/success" />
  <div class="columns is-centered">
   <div class="column is-half">
     <div class="field">
       <label class="label">Name</label>
       <div class="control is-expanded">
         <input class="input is-large" name="name" type="text" required>
       </div>
     </div>
   </div>
   <div class="column is-half">
     <div class="field">
       <label class="label">Email</label>
       <div class="control is-expanded">
         <input class="input is-large" name="email" type="email" required>
       </div>
     </div>
   </div>
  </div>
  <div class="columns is-centered">
    <div class="column">
      <div class="field">
        <label class="label">Message</label>
        <div class="control is-expanded">
          <textarea class="textarea is-large" name="message" rows="5" required></textarea>
        </div>
      </div>
    </div>
  </div>
  <div class="g-recaptcha" data-sitekey="YourRecaptchaKey" ></div>
  <div class="columns is-centered">
    <div class="column is-one-third">
      <div class="field">
        <div class="control">
            <button type="submit" name="submit" class="button is-primary is-outlined is-medium is-fullwidth is-rounded">Submit</button>
        </div>
      </div>
    </div>
  </div>
</form>