Napolitan (ナポリタン, ketchup spaghetti)

Ketchup is the ingredient people mistrust here, so let's be plain about it. Napolitan is not pretending to be Italian pasta. It belongs to yōshoku, the Japanese way of taking Western dishes into the home kitchen and making them answer to Japanese appetite. That makes it honmono, not a joke with red sauce.

The one detail that decides it is cooking the ketchup. If you only squeeze it over hot noodles, it tastes sharp and raw, like a bottle left open on the counter. Let it hit the skillet with onion, pepper, and ham, and the acidity softens, the sweetness deepens, and the sauce turns glossy enough to cling. Butter goes in at the end because its milk fat rounds the tomato and gives the noodles that wet shine a kissaten plate should have.

Use ordinary spaghetti and don't chase firmness too hard. Napolitan wants noodles a shade softer than Italian pasta, because this dish grew around the texture of cafe spaghetti, not bronze-die severity. Rinse or oil the cooked noodles if they must wait, then fry them hard enough that sauce and pasta become one thing. It is quick food, weeknight food, and comfort food, but it still has a method. The method, not the menu, is what makes it sit properly on a Japanese table.