In a saucepan set over moderate heat oil until hot. Add onion, garlic and salt and pepper and cook mixture, stirring, until translucent. Add tomatoes, paste, broth, chiles, and sugar. Bring sauce to a boil and simmer, covered, for 15 minutes. tortillas. In a bowl combine the pork with enough of the sauce to lightly coat. Divide the filling among tortillas, top with the garnishes and roll up.