Buying gravlax is an expensive proposition. Actually, it's easy enough for the home cook to prepare, as it is simply salmon salt-cured in the refrigerator. The challenge is preventing "hot spots." Because the traditional salt cure is dry and has little or no liquid, the fish can develop oversalted areas that are too dry and even a bit tough.
We wanted an easy method for making gravlax that would be evenly moist and tender and consistently salted throughout.
A wet brine in red onion juice ensured that the salt and other curing ingredients were evenly distributed throughout the salmon fillet, producing a moist gravlax with great texture. The procedure was simple enough: We skinned the salmon and placed the fillet and curing ingredients in a zipper-lock bag, thereby maximizing brine penetration and eliminating the need to flip the fillet. All the fish needed was to be weighted down and refrigerated for 12 to 18 hours (depending on thickness.) The gravlax was ready when the fish was no longer translucent and its flesh was firm, almost rubbery, with no give.