1Preheat an oven to 325 degrees F (165 degrees C).
2Stir the hot dogs, Cheddar cheese, relish, ketchup, mustard, and onion together in a bowl; spoon into the hot dog buns. Wrap each sandwich in aluminum foil.
3Bake in the preheated oven until hot, about 20 minutes. Serve immediately.
Footnotes
Tip
Aluminum foil can be used to keep food moist, cook it evenly, and make clean-up easier.