Peel the onions and cut a cross into the bottom to half the vertical depth.
Microwave it in a heat-resistant glass container at 1200W for 2 minutes. (Cooking time depends on the wattage of your microwave.)
Heat dashi soup stock and the cooked onions (from instruction 2) over the middle heat in a small pot. When it is boiled, add and break apart the ground pork, and cook. Remove scum floating in the pot.
Remove the pot from heat, add miso and stir it to be completely dissolved. Reheat the miso soup until it is just hot. Never boil the soup. Serve the soup in a bowl.