Cod With Leeks and Tomatoes
Cut away and discard the root and dark-green leaves of the leeks, then thinly slice the white and light-green parts crosswise into rounds. Wash the pieces in several changes of cold water until there's no more grit at the bottom of the bowl. Drain on paper towels.
Other firm, mild fish, including halibut, sole, and haddock, can be used in place of cod.