the classic is a stilton with a ruby port
The question would be better phrased, what is your best recipe using a red wine because you're changing the flavor of the wine anyway, so you could just look at any recipe with wine in it. you can make a boeuf bourgogne a little spicier if you used port instead of a dry red for instance. Duck a l'Orange works with a port sauce too, just looks a little "darker" then if you'd use gran marnier
but in all honesty
it depends on the ruby port
if you buy something like a warre's warrior, fonseca bin27, taylor ruby, just make a demi-glace out of it and throw it on top of any meat.
a self standing ruby like the rozes or grahams 6 grape is just fine drinking on its own.
The fruit holds up for about a week before it starts oxidizing and you lose the freshness.
warre's warrior is probably best for cooking as would be the dow's ruby since they have less residual sugar compared to the much higher graham's 6 grape or fonseca bin27.