For traditional Zanzibari food, you can't beat Stone Town. Being near the coast, seafood unsurprisingly features on most menus, often seasoned with flavours from around the Indian Ocean. For those with deep pockets, luxury rooftop restaurants are a must, while markets and street-food options abound for those on lower budgets.
Forodhani Gardens is a public park where every evening vendors set up stalls and offer grilled meat, seafood, 'Zanzibar pizzas', samosas and bhajis, all served on paper plates. Meals cost Tsh3000 to Tsh10,000, but prices are not displayed so you may need to bargain. Locals advise against anything that isn't evidently cooked fresh, while lurking papasi (street touts) and piles of rubbish further temper the experience.
Note that during low seasons (April to May and October to November) and Ramadan, many restaurants close or operate with reduced hours.