I prefer to cook salmon (and other fish) in baking paper rather than in aluminium foil - a big piece of baking paper folded in half so that you get two layers.
I sometimes precook/soften/sweat sliced or finely grated vegetables such as leeks, fennel, ginger (or anything else that tales my fancy) and place them under and on top of the fish before folding up the package securely. Gives a delicious flavour and aroma.