El Otro Peñoncito, located a block away from the Plaza de Armas, has tasty Peruvian and Italian cuisine in a small but upscale restaurant. The owner is friendly enough, and the prices are reasonable, although by Peruvian standards they are somewhat expensive.
Restaurant McGrill, on Avenida Geterbo, has cheap set-menu lunches for 7 soles from 12:30 to around 3:00 pm. The restaurant is very clean and hygiene is good. Meals are small but tasty.