Configure your ATAPI CDR as a SCSI device.

Tested on FreeBSD 4.10
Why do this?
Not all CD-R/RW drives are supported by the default burncd software. Check the list first.

You are most likely going to need to reconfigure your kernel. Install the src’s with /stand/sysinstall

Now add, or make sure they already are:
device atapicam
device scbus
device cd
device pass
device ata
to /usr/src/sys/i386/conf/GENERIC (If you are using i386).
Some people including myself like to copy the GENERIC file to a place were they won’t loose it, in order to remember what they configured during their last kernel build. ie /root

Now rebuild your kernel
# cd /usr/src
# make buildkernel KERNCONF=GENERIC
# make installkernel KERNCONF=GENERIC
# shutdown -r now

You should now see you CDR/RW as cd0 as the system boots. (If you only have one SCSI CDROM DEVICE)
example:
cd0: Removable CD-ROM SCSI-0 device
cd0: 16.000MB/s transfers
cd0: Attempt to query device size failed: NOT READY, Medium not present - tray closed

If you do, you are good to go. If not read more
FreeBSD Handbook CDR
FreeBSD Handbook Rebuild Kernel