Alvarinho (Portugal)
Vermentino (Italy)
Albariño (Spain)
Sauvignon Blanc (World)
Rueda (Spain)
With sour cream, mustard, and raw onions,
a semi-dry white wine will work best:
Riesling Auslese (Germany)
Gewürztraminer (France)
Grüner Veltliner (Austria)
Champagne (France)
Metodo Classico (Italy)
Prosecco (Italy)
Cava (Spain)
Sekt (Germany)
Rakfisk is fermented fish, and is usually accompanied by Beer and Aquavit.
A good wine will also do, but steer away from red wine.
The wine should be extra fresh (acidic) and fruity to cope with both fat, salt and umami. Slightly fizzy Alvarinho from Portugal is a very good choice.
A sparkling wine can also be a good match.
Match by color suggests a juicy Rosé.
Rosé wines from Piedmont (Nebbiolo Rosato) often have both fruit and freshness enough to contrast the fat fish.