If the salmon is hot smoked, then you can't go wrong with a Scandinavian dill mustard sauce. If it's cold smoked, I'd probably just squeeze over a bit of lemon and grind on some black pepper. If it's poached, then a creamy creme fraiche dressing with dill and lemon rind or a light tartare-style mayo with a very finely chopped sweet dill pickle, a very finely chopped silverskin baby onion and a few well rinsed, finely chopped small caper berries. If it's tinned I implore you to throw it in the bin forthwith, for nothing will make it palatable.