The roasted pork topping commonly served with ramen is chashu.
Chashu, also written chāshū, is a Japanese ramen topping made from seasoned pork. It is commonly prepared from pork belly or pork shoulder, rolled or left in a slab, and cooked slowly in a sweet-savory mixture that may include soy sauce, sake, mirin, sugar, ginger, and garlic. The finished meat is sliced into thin rounds and placed on top of the noodles.
The name and technique are related to the Chinese dish char siu, but Japanese ramen chashu is often braised or simmered rather than roasted over a flame. That difference explains why descriptions of chashu vary: some menus call it roasted pork, while others describe it as braised pork.
Chashu is a standard topping in many ramen styles, including tonkotsu ramen, but it is not the same as kakuni, which is a chunkier Japanese braised-pork dish. Yakibuta can also refer to roasted pork and is sometimes used nearly interchangeably, yet chashu is the familiar canonical answer for a ramen quiz.