Gather all the ingredients. For the steamed rice, please note that 1½ cups (300 g, 2 rice cooker cups) of uncooked Japanese short-grain rice yield 4⅓ cups (660 g) of cooked rice, enough for 2 donburi servings (3⅓ cups, 500 g). See how to cook short-grain rice in a rice cooker, pot over the stove, Instant Pot, or donabe.
For the beef, I use assorted thin-sliced beef labeled komagire from my Japanese market and cut the slices further into smaller pieces. It works great for gyudon. For higher quality, use shabu shabu beef. If you cannot find thin sliced beef in your local grocery store, you can slice it at home. Freeze a block of fresh chuck or rib eye beef for 1–2 hours and then slice thinly. If the pieces are too large after slicing, then cut them in half. See my tutorial How to Slice Meat Thinly for detailed instructions.
To Cook the Gyudon
Cut ½ onion into thin slices and slice 1 green onion/scallion into thin rounds. Set aside.
Heat a large frying pan over medium-high heat. Add ½ cup dashi (Japanese soup stock), 1 Tbsp sake, 1 Tbsp sugar, 2 Tbsp mirin, and 2 Tbsp soy sauce. Tip: Add more sugar, if you prefer a sweeter taste. I don‘t recommend reducing the amount, as you need it to counterbalance the saltiness of the soy sauce.
Cover the pan with a lid and bring the sauce to a boil. Once the sauce is boiling, add the sliced onions and spread them out in a single layer. Cover to cook until tender (make sure you cover the pan, otherwise the sauce will evaporate).
When the onions are tender, add ¾ lb thinly sliced beef (chuck or ribeye) on top in a single layer and cook until it‘s no longer pink. Skim off the scum and fat on the broth's surface with a fine-mesh skimmer (find it on Amazon and JOC Goods).
To Serve
Divide 2 servings cooked Japanese short-grain rice into individual donburi serving bowls. Ladle the simmered meat, onions, and sauce over the steamed rice.
Top with the sliced green onions and 2 Tbsp pickled red ginger (beni shoga or kizami beni shoga). If you‘d like to top each bowl with an egg (optional), serve with 2 onsen tamago. Alternatively, you can pour beaten egg over the meat when it’s almost finished cooking in the pan (see how I do it in my Tanindon recipe).
To Store
You can keep the leftovers in an airtight container and store in the refrigerator for up to 3–4 days or in the freezer for a month.