Caernarfon is not a foodie destination — the best meals in town are the unpretentious ones: lamb and fish at the older inns, fish and chips on the quay, a sit-down lunch in one of the pubs inside the walls. Welsh staples — laverbread, Welsh cakes, bara brith — turn up in cafés and farmers' markets.
For something a step up, look at Osteria, an Italian place inside the walls that punches above its weight, or the restaurant at Galeri on the harbour. The cluster of small restaurants along Hole-in-the-Wall Street is reliable for a casual evening meal.