{{ $pagesBySection := site.RegularPages.GroupBy "Section" }}
{{ $sortedSections := slice }}

{{ range $pagesBySection }}
  {{ $sectionPage := page.GetPage .Key }}
  {{ $sortedSections = $sortedSections | append (dict "sectionPage" $sectionPage "pages" .Pages) }}
{{ end }}

{{ range sort $sortedSections "sectionPage.Weight" }}
  <h3>{{ .sectionPage.Title }}</h3>

  <ul>
      {{ range .pages }}
      <li>
        <a href="{{ .Permalink }}">{{ .Title }}</a>
      </li>
      {{ end }}
  </ul>
{{ end }}