I cook salmon this way & it is so tasty. I've done this to other fish as well & it is good, but the salmon is
put it on alum foil, cover the fish with thin slices of butter then coat generously with seasoning salt. Wrap up completely in the foil. Bake at 400 for approx 20 min. I check at that point to see if it is done. Fish is done with it is flaky with a fork.
I buy most of our fish at Costco. You can get a large bag with several filets for a really good price.