I looked hard for this in Sonar myself and feel pretty sure it can't be found there. I do know SONAR will work with soft synths that use tuning tables, although any scale you use needs to be mapped onto a traditional 12-tone piano keyboard for things like Piano Roll view. I believe SONAR only allows pitch adjustments by half-tone, nothing finer.
Scala, available for free on the Web, provides literally thousands of tunings as well as the ability to customize your own. It can apparently send tuning tables to any synth, hard or soft, that can receive them. Many people have had good experiences with it. That said, I've never been able to get it to work.
Reaktor works with tuning tables, but not Tassman. A good plug-in for using tuning tables in Reaktor is in their user library.