docker postgres backup creates an empty file when run as a cron job

I'm trying to create a cronjob that creates db backups every night.

My crontab has the job: * * * * * /home/user/scripts/backup.sh (have it set to go off every min for testing)

In backup.sh, I have:

docker exec -it dbContainer pg_dump -U username -d dbName > /home/user/backups/testingBackup.sql

The file is always empty:

-rw-rw-r--  1 user user    0 Jul 14 08:39 testingBackup.sql

However, if I run the file on my own and type the command /home/user/scripts/backup.sh, it is not empty:

-rw-rw-r--  1 user user 30813 Jul 14 08:45 testingBackup.sql

I feel like it makes sense something is off on the permissions, but everything is done from the "user". I haven't done anything from root such as sudo crontab... sudo /home/user/backups/testingBackup.sql, etc.

I am confused as to why in one scenario, the resulting file is empty, and in the other, it is not.

Thanks for any help