Berta's is a welcome change from the nacho-and-fajita joints that dominate Old Town dining, though the small room can attract as large a crowd on weekends. Housed in a charming, basic cottage tucked away on a side street, Berta's faithfully re-creates the sunny flavors of Central and South America, where slow cooking mellows the heat of chiles and other spices. Everyone starts with a basket of fresh flour tortillas and mild salsa verde, which usually vanishes before you're done contemplating such mouthwatering dishes as Guatemalan chilimal, a rich pork-and-vegetable casserole with chiles, tomatoes, cornmeal masa, cilantro, and cloves. Try the Salvadoran pupusas (at lunch only)--dense corn-mash turnovers with melted cheese and black beans, their texture perfectly offset with crunchy cabbage salad and one of Berta's special salsas. Or opt for a table full of Spanish-style tapas, grazing alternately on crispy empanadas (filled turnovers), strong Spanish olives, or Pincho Moruno, skewered lamb and onion redolent of spices and red saffron.