The Real Madrid man sent Robert Almer the wrong way but could only look on agonisingly as the ball came back off the post with 79 minutes gone.
In fact, it proved to be a night to truly forget for the superstar as he missed several gilt-edged chances in front of goal and even had a header ruled out for offside.
The stalemate means Portugal have yet to record a victory in the Euros and will need to beat Hungary in their final group game to guarantee progression into the final-16.
Though Austria were unable to find a winner of their own, they celebrated the draw like a victory. A win over Iceland could secure their place in the latter stages.
Portugal started the game at a frantic pace and created several chances but were let down by a lack of proficiency in front of goal. They had more have had more shots on goal in the opening half an hour of a match at the Euros than any other side.
Their best opportunity fell to their star-man Ronaldo but the Real Madrid forward uncharacteristically sent the ball wide from eight yards out.
Austria looked extremely vulnerable in defence but provided a threat on the offence and they almost took the lead against the run of play when David Alaba’s free-kick was headed off the line by Vieirinha.
The frustration grew for Portugal – and Ronaldo – after the break. Goalkeeper Robert Almer produced successive saves to deny the Portuguese number seven.
Then, on 78 minutes, Ronaldo was handed the most glorious chance. Lukas Hinteregger hauled him down and the referee had no choice other than to point to the spot. Quite unbelievably, his shot struck the post.
Somehow Austria hung on for a crucial point and they live to fight another day. As for Portugal and Ronaldo, their search for a win still goes on.