I don't have a recipe, but I can tell you what and how I do it: I use salmon or trout, but I think many other kinds of fish go as well.
I chop a few shallots and add to the pan, salt and pepper the fish fillets and put on top of onion. Drizzle a little lemon juice on top, and pour a cup of dry white wine on the side. Cover with aluminum foil and bake until done. I the carefully pour off all the stock to make sauce. I add sour cream or creme fresh, let simmer for a few minutes, add a knob of real butter and stir. If you want the sauce a little thicker, use cornstarch with a little cold water. Then balance the taste with a few drops of tabasco sauce and probably a little more lemon juice. The sauce should be a little tart and very creamy.
You may add copped dill and/or a small handfull of cooked and shelled shrimps for a variety, or you may add a litttle dill to the fillets, if you like that taste.