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Configure an external URL to run cron at admin/config/system/cron .
Visit Pantheon's New Relic by clicking on the "New Relic" button in the Pantheon's Site's Dashboard
Go to "Synthetic monitoring tab on the right-hand menu
Click "Create your first monitor"
Click "Create a new Ping monitor"
Use the name "Drupal Cron", with the tag "cron"
Set the URL to be Drupal's cron URL at admin/config/system/cron
Click "Save"
Now you will be able to monitor when the cron is run directly through New Relic.
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