Maybe one of you jazz guys can help me out with this one...

In a 13 (b5) chord, would you use a lydian dominant chord over it?

Mind you, it has a flat five, so there is no natural fifth.

Just wondering what the traditional answer is.

I don't think there is any "natural" scale for that chord. If you just sort of map out the pitches --

C D E F Gb A Bb C

-- the little chromatic sequence there makes it so that no normal scale, or mode of a scale, will suit it. I think "normally" with a 7b5 chord I would be inclined to flat the 13th, too, and then use the whole tone scale or something. But if confronted with that chord as is (and if I had a minute to think about it), I would do the common tone thing and take the chord tones

C E Gb Bb A

and fill in the remaining notes from the key of the progression. I expect that the 11 will be an avoid note in any case.

I don't think there is any "natural" scale for that chord. If you just sort of map out the pitches --

C D E F Gb A Bb C

-- the little chromatic sequence there makes it so that no normal scale, or mode of a scale, will suit it. I think "normally" with a 7b5 chord I would be inclined to flat the 13th, too, and then use the whole tone scale or something. But if confronted with that chord as is (and if I had a minute to think about it), I would do the common tone thing and take the chord tones

C E Gb Bb A

and fill in the remaining notes from the key of the progression. I expect that the 11 will be an avoid note in any case.

Yeah, I agree that that particular chord calls for a synthetic scale. Thanks for your advice!