Bertlin1
I've asked the same question about Sonar X2. I keep looking for a way to change the tempo ratio like I could in older versions. Why would they take that out? The only reason I would upgrade to a newer version of Sonar is if they were to put that functionality back in to it. Otherwise, I'm a bit of a low level user that doesn't need most of the stuff they've been adding to the newer versions.

I haven't tried this recently, but if you have an all MIDI project, it may work.  That is to say, SONAR can't host any audio...not even from soft synths.  All your MIDI needs to go to external devices.

8.5.3 was the last version that had it. Just one more item in the long list of things we lost with the X series that was never replaced.

HI:)
 
you can define Keystrokes for Tempo 1,2,3 but I can't get it to work:(
So this function is definetely gone...
 
Bassman.
 
 

I can't answer for X1, but the newer versions of Sonar (Artist, etc.) have restored the tempo ratio commands. They, however, are not as apparent as they were in the pre-X versions of Cakewalk. You can assign them via keyboard bindings and/or buttons on the custom module of the control bar. (Right click on the custom module and choose "commands.")
 
FWIW, remember that this feature will only work if the project clock is set to "internal."

Yes, this feature became mostly obsolete with the advent of Audio support because all the audio would need to be stretch-enabled in order to follow tempo changes. It only works in a pure MIDI project driving external hardware synths with Project Clock set to 'Internal' (PC System clock), and using the MIDI metronome.