Clean the salmon head, split it in half, and marinate with a little seasoning powder, fish sauce, black pepper, and green onion. Cut the tomato into wedges and slice the asparagus into small pieces. Bring about 1 large bowl (about 4 cups/950 ml) of water to a boil, add the salmon head, then add the tomato and asparagus. Season to taste.

Finally, add the bean sprouts. If you like it spicy, add a little sliced chili. Turn off the heat, sprinkle black pepper on top, and enjoy the soup hot.