After the tools report a successful burn, the disk appears to be blank. I tried the burn with brasero and k3b multiple times.
Any suggestions to actually burn the CD?
I had once that problem: - disc ain't closing properly - disc is low quality - lens from burner is worn out
If the disk is really burning (you can see the tracks) check other it with different driver.
Use root privileges(may not be the best option, but this seems to be the only solution right now)
Open terminal and type sudo k3b.
I was on 64 bit Ubuntu 16.04. Opening the application this way solved the issue for me.