It's honestly really really easy. Probably the easiest way to prepare salmon. In the evening you take raw salmon fillet, you put plenty of sea salt on it, a tiny bit of sugar and hefty amount of dill. Put in the fridge. In the morning, it's done. Slice it into nice slices and eat as is or put on rye bread with some onion. I never bother with the sauce, seems superfluous and just hides the salty salmon taste.

I don't know what sort of restaurant would have it. Outside of some specialty Swedish kitchen or Nordic or Norwegian one, could be in some sea food one as an appetizer I guess? But almost always the ready made ones or even ones at restaurant go light on the salt and rely on the sauce. It's much better imo when you make it yourself.