This is simple, but it does take some attention.
First, get a wild salmon filet. ‘Caught that day’ is best, but frozen filets are perfectly good. Just make sure it’s wild salmon and not farmed (Atlantic) salmon. Around here, wild salmon is $7 or $8 per pound. How big depends on how hungry you are. I usually like a half-pound one for dinner, which is really two servings but that’s what I like. I cook a pound and have the other half the next day.
Make a little tray out of aluminum foil. (Why dirty a pan?) Put the salmon skin-side down on the foil. Sprinkle it with a little kosher salt and some freshly-chopped dill. Bake it in a 325º oven for 20 minutes or so, until it flakes. (Cooking time depends on thickness.)
While the fish is cooking, melt some butter (say, 2 tablespoons) in a small pan. You can finely-chop onions and put a little in with the butter and a pinch of kosher salt. Onion is not necessary, but I like to use up the leftovers I tend to have. If you’re not using onion with the pinch of salt, just melt the butter. Add the same amount of flour as you did butter. Mix it up. This is called a roux. You want to toast it a bit, but since this is a white sauce you don’t want to toast it dark. Just toast it for a couple of minutes, stirring frequently.
Add some cream and stir until smooth. Add a couple of tablespoons of freshly-chopped dill, and a bit of kosher salt to taste. (You don’t want it very salty.) Keep stirring as the sauce thickens. Once it’s the desired consistency, add some lemon juice. I was experimenting, and I was afraid the cream would curdle when the lemon juice was put in. It didn’t. I’m guessing that’s because it was hot and thick and the butter had been incorporated and all that. Or maybe it was because I was using lemon juice out of one of those plastic containers instead of a fresh lemon. I don’t know. Anyway, it worked.
Take the fish out of the oven, put it on your plate, and put some of the white sauce on it. Maybe you have some boiled red potatoes and steamed asparagus to go with it. The sauce is good with those, too.
Simple recipe, few ingredients, not too expensive; but if you ‘smoke up the house boiling water’ you’ll need to make a leap of faith. Just watch the temperature while you’re making the sauce, and remember to stir.