Naranja Agria is used in Latin American cooking. Elisabeth Lambert Ortiz in her "Book of Latin American Cooking" suggests one third lemon or lime juice to two thirds sweet orange as a substitute. You could also use 1 teaspoon cider vinegar to 3 Tablespoons sweet orange juice. The naranja agria is actually the juice of a Seville orange. Most of the Seville oranges are shipped to England for the marmalade. The Seville orange has a sour bite.