Antica Hostaria Massa is a short walk from the palace and a reliable place to eat after a morning in the Reggia. The kitchen stays close to local tradition: expect mozzarella di bufala from the surrounding plain, pasta dishes with tomato or pork ragù, and second courses built around braised or roasted meats. The wine list leans on Campanian producers, which is exactly what you want here.
The dining room is unpretentious, the portions are generous, and the pace is unhurried — this is not the place if you are trying to catch a train. Prices are reasonable by the standards of a restaurant this close to a major tourist site. Book ahead on weekends and in summer.