Different problems result in different sounding noises. If it's a pulsed snoring (or sawing) sound zzzz, ................. zzzz .............. once per crank rotation as you describe, it's possibly a wobbly chainring, or play in the spindle or crank allowing the crank to deflect out at the top when you load the pedal.

A more grinding sound could be a bearing issue, though that doesn't tend to pulse in rhythm as clearly. However BB bearing noise does get worse at max power input (horizontal pedal) because the chain tension pulls the crank back maxing the bearing load.

There are other sounds, but that's for starters, and might point you in the right direction.

If you don't find the problem, you might want to repost with a better description or better yet a video (audio) so we might hear the problem outselves.