Mesón de Bari, on Calle Hostos between Luperón and Salomé Ureña, is a good choice for Dominican cuisine in the Zona Colonial. Set over two floors with exposed wooden beams and an eclectic mix of paintings adorning the walls, the restaurant / bar caters to tourists and locals and the menu is translated into English and French.
The house speciality is stewed crab, served with (almost all) the shell removed and full of flavor. We also tried spicy Dominican sausages and some surprisingly tender goat strips, and there is a whole range of traditional seafood and steak dishes on offer. Make sure to leave room for dessert: The dulce de coco con leche was tooth-dissolvingly excellent.
It's not a cheap meal — you could easily drop $100 on a meal for two — but it is worth it.