Rewritable CD's (identified as CD-RWs) can, obviously, be rewritten. While they remain a little more expensive that CD-Rs (perhaps twice the cost) they can be reused many times. But note that not all home audio CD players can read CD-RWs. One that can is the Marantz CD5000.
Burning a CD-RW is essentially no different to burning a CD-R. In fact cdrdao identified the CD-RW correctly and dropped its recoding speed down to 4x to suit the CD-RW, all automatically.
To re-record the CD-RW you need to blank it first. With cdrdao this is done with:
$ cdrdao blank
Although the command returns quite quickly the blanking process continues for quite some time while it performs a long write (you can instead do a minimal blank with the option -blank-mode minimal. After this has completed you can burn to the CD-RW as if it were a new blank CD-R.