Our first night in Lisbon next week is our 29th anniversary. We are staying near Restauradores/Rossio. Any suggestions for a special Portuguese restaurant?

We had a very nice meal recently at Solar dos Presuntos, just off of Avenida da Liberdade.

solardospresuntos.com

For a fun and delicious seafood meal but maybe not for an anniversary celebration, try Cervecjaria Ramiro, www.cervejariaramiro.pt

"Tavares Rico" is the place. THE historical restaurant of Lisbon. Already mentioned in "The Maias" the 19th century novel of Eça de Queirós.

I can thoroughly recommend:

RESTAURANTE CASA DO LEÃO

The food was excellent as was the service and the views. The blurb says:

Located within the ramparts of St George's Castle situated on the top of the Alfama hill , the oldest part of Lisboa, this restaurant offers one of the best views over Lisboa as well as menus of the best traditional Portuguese gastronomy.

"Solar dos Presuntos" is indeed a good recommendation for Portuguese cuisine nearby but I'm not sure it has the right ambience for a wedding anniversary...
I recommend "Tágide," with wonderful city views, just up the hill from where you're staying. Tavares is another good option but be warned that it's Michelin-starred and therefore quite expensive. Two alternatives would be Belcanto and Largo (they're right next to each other).
Take a look at this selection of restaurants in the city (with great photos which may help you decide!): http://www.lisbonlux.com/lisbon-restaurants/

Try Belcanto Restaurant from Chef Jose Avillez