overwrite backup every day?

I want to schedule a backup that runs every night at the same time. I need to limit the amount of space it uses, so I want to overwrite the previous backup every time.

With retention rules I can set the option to overwrite backups that are older than 1 day, but if I understand correctly that will leave me with 2 backups at all times.

How can I overwrite the previous night's backup every time, before the new backup starts?

Thanks!