Carefully clean the yellowtail fish; remove its internal organs and scrape off the scales. Place the fish in a wide pot and add enough cold water to completely cover it. Optionally, you can enrich the flavor of the fish by adding a few pieces of bay leaves or 1 slice of lemon to the water. Let it boil over medium heat. When the water begins to boil, reduce the heat and poach the fish for approximately
10-15 minutes, until the meat easily separates. Be careful not to overcook the fish, otherwise it may become dry and lose its flavor.