The standard-bearer of Salvadoran food, a pupusa is a flat, pan-fried pocket of corn dough traditionally stuffed with cheese, beans or meat, then served with mild salsa and curtido (a tangy cabbage slaw). Maria and Juan Vasquez serve them with and without meat at their 3 in 1 Restaurant in Indianapolis.
Available in large supermarkets, corn masa flour (masa harina) is the primary ingredient in Latin American staples like tortillas. It's made from dried hominy--corn that has been treated with lime (calcium hydroxide). Cornmeal is not a substitute. Maseca is a popular brand.
In a large saucepan, combine 1 pound whole Roma tomatoes and enough water to cover. Bring to a boil; reduce heat. Simmer, uncovered, until tomatoes are soft and the skins have started to burst open and peel, about 10 minutes. Using a slotted spoon, remove tomatoes from water; let cool and remove skins. Do not discard cooking water. In a blender, combine tomatoes, 1/4 cup chopped white onion, 1 clove garlic and 1/2 teaspoon salt. Cover and blend until smooth. If necessary, add some of the tomato cooking water to make smooth. Do not add too much or sauce will be watery. Transfer mixture to a saucepan. Bring to a boil; reduce heat. Simmer, uncovered, until slightly thickened, 20 to 30 minutes. Let cool before serving.
In a large bowl, stir together 1 cup water, 2 tablespoons white vinegar, 2 tablespoons fresh lime juice and 1 1/2 teaspoons salt. When salt is dissolved, taste mixture; add more salt or vinegar as needed. Add 5 cups shredded green or red cabbage, 1/2 cup shredded carrot and 1/4 of a fresh jalapeño pepper, finely chopped. Mix well to coat. Let stand at room temperature until slightly softened, about 1 hour. Cover and store any leftovers in the refrigerator.