Hi  @dhunt2 ​ - Yes, you can do this.  And to give credit where credit is due, the second bullet item listed under  @kmeeusen ​'s response to a somewhat similar (though broader) question provides what you need:  .  This topic has flared up from time to time in the Community--mostly for how to given an entire quiz that is worth extra credit points (no answer on that one yet, though everyone hopes improvements are coming soon via the new quiz engine), but a specific question is fairly easy to pull off.

Basically, just add your extra credit question, and perhaps explain in the question that they can earn up to xx number of points by answering it correctly.  The question itself, however, must be worth zero points.

Then, when grading it, you can simply manually adjust the points on that specific question using the text box editor or spin control box next to the score while looking over each student's quiz, as shown below:

Canvas does not "care" if the total score is more than what the quiz itself was worth...it will still dutifully tally the total points scored for each student.

Hope this helps a bit.