What type of restaurants are you looking for?
In the Punta Cana area you have quite a few options, however, they are not that cheap ($$$).
You have options inside of Cap Cana such as Mitre (my favorite, the food is fantastic). Also inside of Cap Cana is Sanctuary Hotel which has a few restaurants that are also open to the public such as David Crockett (steakhouse), Wok (asian fusion), Blue Marlin (seafood) along with a few others. I also received a promotion email recently from another restaurant on the Cap Cana Marina called Aquamare or something like that. The prices seemed reasonable, however, I have never eaten there. You can check Cap Cana's website for more info on them. There is also another restaurant called La Yola in Punta Cana (designed by Oscar De la Renta) and I believe they have a website also.
If you would like more reasonably priced restaurants (however, the taxi ride may be a bit more) you have Jellyfish, Hurrican Cafe, El Pulpo Cojo and Capitan Cook (not my fav, but tourists love it) and I'm sure there are some that I am missing which I'm sure other people can fill you in on.
Have a great trip. Tortuga Bay is beautiful. Let us know how you like your trips and which restaurants you tried.
Enjoy!