Salmon isn't the only fish that can be cured with salt and sugar to great effect. Tuna becomes silky smooth and luscious when cured the same way. Serve the results with cream cheese and rye bread like traditional gravlax, or mix things up and make a quick sauce of homemade mayonnaise with a bit of freshly grated horseradish or wasabi (or ground wasabi) in place of the garlic for a great kick. We like to use troll-or poll-caught pacific albacore tuna since it is a sustainable fishery and the resulting fish aren't overloaded with mercury, but this recipe will work with whatever fresh tuna you choose. Feel free to cure more than one loin to serve a crowd. Simply increase the amounts of everything else accordingly.