This is a light bento item that is great for summer. By adding a bit of vinegar, you can prevent contamination and bacteria spreading in your bento.
I add vinegar to bento rice in the summer to prevent spoilage, so I tried doing the same to my hamburger steak.
Step 1 - Adjust the amount of vinegar according to the amount of meat.The linked recipe is for an Italian style hamburger steak.The sauce is great even without the red wine.
Enjoy Japanese food around the world.