The /tmp/crontab.wFM7eq file is just the temporary buffer you're editing, once you've saved it in the editor, it will become the new crontab-file for the user you're editing for.
The first time you edit a user's crontab-file, it typically will be empty (or contain a comment about the various fields). So if this was the first time using crontab -e for this user, this is correct behavior. Once something had been added, this will show the next time you edit the file.
The master-crontab file - /etc/crontab - you probably must edit manually with sudo nano /etc/crontab (remember that what is in /etc/crontab.d is "added" to the /etc/crontab).