Classic Tortilla Soup

unpeeled

large

small, or a 1-inch-thick slice of a large white onion, peeled

medium, stemmed, seeded and torn into large pieces

torn into 1 - inch pieces

for shallow frying

cut into 1/2-inch-wide strips

or regular sour cream

peeled and diced into 1/2- inch cubes or slices

or mild feta, crumbled

optional