Re-reading your post, perhaps you were just looking for cake recipes. The two below are not cakes - though one is a dessert - but they do use the Port!
The most immediate thought is “reduction with some juniper berries and rosemary, to serve with venison steak” (we have a fantastic game butcher about 10 miles away, and venison is cheaper than beef!). Cook the steak as you normally would, when done, put in a warm place to rest. Chuck 100 ml of Port (per 500 gr of steak) in the steak pan with the cooking juices of the meat, a few crushed juniper berries and a few needles of rosemary (quantity depends on what flavour you like). Season well with salt and pepper (unless you already seasoned the steaks in the pan), and reduce on the highest heat to ⅓ of the volume (it will start to look quite thick and syrupy) - put the steaks back in and coat through, or decant into a small bowl/sauce boat and serve on the side.
Another simple option is zabaglione - traditionally (in Italy) made with Marsala, but it comes out nice with Port too. For each person:
1 egg yolk - at ambient temperature
1 tablespoon (12-15 grams) of sugar - for a dry wine; if the wine is very sweet, decrease the sugar to 8-10 grams; if using table wine increase to 15-20 grams
4 tablespoons (48-60 ml) of wine (Marsala, Madeira, Port, Sherry or full-bodied red table wine all work well)
If you have a double boiler, put yolks and sugar into the top bowl and beat until pale yellow and creamy; in the meantime, heat the bottom bowl. Add the wine, put the top on the bottom and keep whisking with a hand or electrical whisk until the mixture fluffs up and forms soft peaks. A pan of nearly-boiling water and a metal bowl work just as well as a double boiler.