Butadon, which features sliced pork and onions, is a quick donburi (rice bowl) to make, and the recipe varies from cook to cook. I’ve seen versions without onions, for instance. Once the rice is cooked, the rest of the dish takes less than 15 minutes to prepare. You don’t need to marinate the meat, and the pork and onions are cooked together in one pot. I like to use skinless pork belly, which, because it’s so layered, stays moist; buy a leaner cut, if you prefer, but take care not to overcook...