Cut the bacon into strips. Line a roaster alternately with strips of bacon and flakes of butter.
Rub the carp inside and outside with salt, place on the bacon and the flakes of butter. Alternately distribute strips of bacon and flakes of butter on the carp. Place the whole peeled onion next to it.
Bake in the preheated oven over medium heat (approx. 160 - 175 ° C) for about 45 minutes. Sauerkraut and boiled potatoes taste good with it.