To create a tempo map in Sonar you can use the Fit improvisation feature under the file menu. The way that it works is like this.
Add an audio file you would like to create a tempo map for. In our example we will use a short 1 bar long file for brevity, (image below) but you can use one that is song length.
Now create a MIDI track.
Play notes on the MIDI track that correlate with the beats of the audio file. Our file is in 4/4 time so we record quarter notes. Make sure the first MIDI note lands at the very beginning of the song.
Once you do this go to Process / Fit Improvisation.
A series of tempo changes will then be created allowing the songs MIDI tempo to accommodate the audio region.