Dar has lots of great restaurants, it's been too long since I was there to recommend anything with any confidence, although I used to love Barbecue House, a tandoor place, and there is lots of excellent seafood there as well.
I was in Zanzibar more recently, in Stone Town I can recommend Two Tables for homestyle cooking (it's in someone's house, a very strange place with a set menu but consistently excellent food. I also ate at a nice new seafood restaurant on the second floor of a building just near the Old Fort, but the name of the place is escaping me. It was pretty good. There is excellent Italian ice cream at some other places along the waterfront. The Forodhani gardens have excellent food, and also a great place to walk around and soak up the atmosphere. A long time ago I also ate at the restaurant on the roof of Emerson and Green's. I remember it being excellent, but that was many years ago. Monsoon was also pretty good.
On the East Coast of Zanzibar, a hotel called Pongwe Beach has generally excellent food. The menus are set, with only a few options, but are very good. In Uroa, Uroa Beach hotel, a tiny little place, serves up excellent Zanzibari cuisine.
In Zanzibar, you must go to Forozani at night where you can pick and choose whatever you'd like to eat from the many tables set up infront of the ocean. My favourites were "pizza" both kheema (ground beef) and banana chocolate! very delicious. There is also beef and chicken skewers, and tons of sea food.
Another specialty of zanzibar is something called Mandazi, which is like a lightly sweetened doughnut. The coke there is made with sugar, not corn syrup and comes in glass bottles. Don't know why but bottled coke is so much better than plastic or cans!!!
Regarding Mtoni Marine, this is still my all time most relaxing moment in my whole life. Sitting infront of the ocean with a bottle of coke was amazing. No need to talk, just take in the view.
The sugarcane juice is amazing, if you read the other post the poster suggests using your own bottle. We saved our water bottles and had them filled with the sugarcane/ginger/lemon juice. I think this is around 500 shillings, but it was so good we took it back to dar with us. Also the coconut juice is supposed to be very good but once i tried the sugar cane I didn't want to have anything else.
Im not sure of the name of the restaurant, and I realize this is so vague, but there is a restaurant that faces the ocean soon after you exit the boat. There, we had a peppercorn steak that was so good I still remember it from two years ago. I think one of the most amazing parts was that it was 6000 shillings ($6). Get this with the fresh cut french fries. Hmm to better describe the location, it is on a patio. LOL sorry i know this is not helpful but if you see soemthing like this try it.
In Arusha, there is a restaurant called Khans, one of my friends whom I was speaking to on Wednesday asked my how I could have missed it. My cousins told me about zai-gai or chips-mayai which is fries that are coated in egg and refried. There is a restaurant there called mcmoodys. This is their version of mcdonalds and they dont' know exactly how bad it is. Don't try it thinking of a taste of home.
In Dar, I think the thing to try would be all the various street stalls which have barbeque'd chicken and beef skewers, called mishkaki. YUM! Now I want to go back!
Please post on your return and if you have any more questions :)
Just returned from two weeks in Tanzania. A fantastic experience, though the fauna of the national parks and the beauty of the beach overshadowed the cuisine a bit.
We arrived in Arusha and immediately asked about trying local specialties. We only knew a bit about the nature of the food from Lonely Planet. Our guide suggested asking a cook to prepare machalari, a beef and plantain stew. We bought a big bunch of green plantains at a market in Arusha, where we also saw goats being butchered openly while hanging from the walls of huts, a vivid experience. He said we could get roasted goat there, but would have to wait the better part of an hour, so we decided against it, eager to see some animals live. For the first week of our stay we were in safari camps, which tended to cater to the european taste, so we had to make special requests for ugali and sauce. We found this Tanzanian staple bland on its own, but quite good as a starchy accompaniement to beef and vegetable stews. Later, we tried the machalari which was filling but also somewhat bland for us, especially since our concept of East African food was informed by spice-laden Ethiopian, Eritrean and Somali food prepared in the United States. We did have some decent South African white and sparkling wines, and while the local beers were almost flavorless, it was refreshing after dusty hot days in the car.
The cuisine on Zanizabar was a bright and welcome change from the mainland. We were somewhat captive in the begginng since we were staying at a resort type place on Matemwe Beach with fixed menu breakfast and dinner included in the rate. Fortunately, the chef was well grounded in swahili and zanizbari cuisine while having some European training, which lended itself to a sort of local/continental fusion that was often quite good. Fresh fish with avocado sauce and chips, barracuda carpaccio and grilled white snapper were very nice. Some of the combinations, like peanut butter cake with passion fruit sauce, didn't quite work. The best meals were decidely local and heavily indian influenced, such as the seafood curries, the fresh chappatis, and fantastic samosas, served with fresh garlic, tumeric, coconuts, and ginger grated as toppings. We relished the breakfasts of wonderfully sweet yet firm-textured mango varieties that aren't available in the US (it seems here the stringy, pine-scented alphonse is the only type that can be readily obtained), along with papaya, pineapple, small donuts with cloves inside, passion fruit juice, sausage and eggs with pili pili. We also enjoyed grilled fish kebabs, seafood fritters, and the highly addictive batata bhanjis, mashed potato fritters with fresh chili and a tangy citrus flavors. Desserts included dates, and other arab-tasting seed and nut based sweets.
In Stone Town we were set free. We had lunch at Monsoon Restaurant, reccomended by the tourist guidebooks, with a menu that proclaimed it was "ultimately swahili". We dined comfortably on the floor upon pillows and removed our shoes as in a traditional or kitschy Japanese place. The best dish was pwezaa, octopus cooked with coconut milk, served with collard greens, sweet spiced chickpeas, sweet potatoes with ginger, and chapatitis. As others have mentioned, dinner at the Forodhani Gardens stalls is an essential experience. We tried lobster, shark and snapper mishikaki, skewered octupus and calamari, baseball sized falafel, and more batata bhanji, all grilled up over a wood fire. The massive crab claws were the sweetest I've had. For dessert we tried the famous zanzibar pizza, chappati dough with chocolate and bananas, fried with ghee over a wood-fired wok. A delicious bomb of calories.
If we ever return to Stone Town, I saw a Goan restaurant that looked quite intriguing.