Soak the oatmeal in water for 5 minutes.
Finely chop the onion.
Heat sesame oil in a pot and sauté the onion.
When the onion becomes translucent, add the tuna and stir-fry.
Add the oatmeal and water, then bring to a boil.
When the mixture thickens like rice porridge, season with salt.
Serve in a bowl to finish.