code: public function execute()
      {
          $output = $this->layoutFactory->create()
              ->createBlock('Fastly\Cdn\Block\Dashboard\Tab\Stats\Historic')
              ->toHtml();
          $resultRaw = $this->resultRawFactory->create();
          return $resultRaw->setContents($output);
      }
docs: Return historic stats
  
  @return \Magento\Framework\Controller\Result\Raw