A combination of:
1. Commands to sit/lay down while the cat is in motion, and commands to leave the cat alone after an initial sniff.
2. Corrections for getting up to follow the cat (because this causes the cat to run, which causes Jack to chase) or interacting with the cat beyond a quick sniff (and ignoring the leave it).
3. Praise for leaving the cat alone, sniffing the cat and walking away, or choosing to come to us for attention instead.
4. But the coup de grace is sharing raw hamburger together about a foot away from each other (the trick is reminding Jack not to steal the cat's meat since the cat eats slower).
After practicing the above over the last couple of months, he's comfortable laying next to the cat and ignoring it, and the cat is comfortable with the dog being close to him.
Keep in mind this is working best with our very social and confident male cat who truly doesn't care about strangers and is hardly intimidated by the dog. Our other cat is skittish and doesn't really want anything to do with the dog. We'll have to try working with her when Jack is older, calmer, and extremely obedient.