Problem is, these are not homophones for me. Nor are they for a good many speakers of North American English. For those like me, these words are:
Don = [dɑn]
dawn = [dɔn]
The vowels are different. The vowel in Don is low, back, and unrounded. The vowel in dawn is mid, back, and rounded. Two different vowels, two different words, not homophones. I and those like me also distinguish the pairs cot - caught, knot - nought, bot - bought, rot - wrought, and others.
The [ɑ] - [ɔ] merger is a regional feature of American English, as shown in this map*:
So, Alex Trebeck, be careful about what you claim are "homophones."
*The map is from the University of Pennsylvania's Phonology Atlas.