Cut beef into bite-sized pieces.
Slice the onion.
Heat oil in a pan and stir-fry the beef.
When the beef is half cooked, add the onion and stir-fry together.
Season with soy sauce, sugar, and cooking wine.
Place the stir-fried beef and onion on top of the rice.
Optionally, sprinkle chopped green onion and sesame seeds.