The Melodyne drag-tempo-to-timeline feature just enters tempo changes in SONAR's tempo map. You can go to Views > Tempo, select all the tempo changes and delete them.
To find the original tempo:
- Start playback with no click sounding.
- Count out 4 measures in your head, and stop the transport on the downbeat of bar 5.
- Shift+M to open Set Measure Beat At Now, enter measure 5, beat 1 and OK.
SONAR will reset the initial tempo to make that beat hit that absolute time in the recording. If the song was originally recorded to a click with a whole-number tempo, the calculated tmpo will probalby be within a few tenths. If so, you can change that initial tempo to the whole number vlaue, and you should have good sync.
This all assumes that the audio clip is trimmed so the first down beat in the track is right at 1:01:000. If there are pickup beats, you'll need to align the first downbeat to 2:01:000, and use Shift+M to 'pin' that point before counting out the 4 measures to 6:01.