cupper-hugo-theme/layouts/shortcodes/blockquote.html

{{ $quote := .Inner }}

<blockquote class="blockquote">
  <p>
    {{ $quote | markdownify }}
    {{ with (.Get "author") }}
      <br>
      <span class="author">&mdash; {{ . }}</span>
    {{ end }}
  </p>
</blockquote>