Clean the fish and marinate with 1 tablespoon fish sauce, seasoning powder, sugar, and chopped green onions. Mix well and let sit for 10 minutes. Slice the tomatoes, asparagus, and mushrooms. Bring a pot of water to a boil.

When the water boils, add the fish. Let it simmer for a few minutes, then season to taste. Add the tomatoes, asparagus, and mushrooms, and stir gently. Finally, add the chopped dill and turn off the heat.

Ladle into a bowl, add black pepper or chili if desired, and serve hot.