“Tekka” means “Tetsu (Iron)” + “Ka (Fire)” though its pronunciation changes when they are combined. Maguro (Tuna) looks like a burnt iron (red), which is where the name “Tekka” comes from. “Tekkadon” and “Sakedon (Salmon Donburi)” sometimes come with sushi rice (vinegard rice) depending on regions or sushi bars. However, it is sashimi, not sushi, on the regular rice, not on vinegared rice after all.
(A Variety of Tekkadon)
(You can make one at home as long as you get sashimi!)