Mackerel in 3 minutes

Soak onion husks in water for a while. Then put it on the fire and add salt. You need 5 tablespoons of salt per liter of water (if you need more water, then salt, respectively). Boil the salted onion water, put the mackerel and cook for exactly 3 minutes! Then throw the fish in a colander and you can eat.

The fish is small and has managed to boil completely. Although at first I was also confused by the fact that it only took 3 minutes to cook. If the fish is large, then it can be cut lengthwise so that it is exactly cooked or pierced with a knife in several places.