I hate raw onions. I should say they also don’t like me. I like relish and brown mustard best on my dogs.The question is an abomination.
Each of ketchup and mustard on a hot dog is blasphemous unless you are under 6 years old. For an adult or an older kid, the only correct answer is part of what univee says: sweet relish and onions on a hot dog, maybe chili to go with it. Hell, I put relish and onions in my chili, so I guess chili on a hot dog is OK so long as it's accompanied by onions and sweet relish. Same with burgers.
I learned this from eating grill cheese sammiches at the Columbus Bar in C-bus. The old regime served them with sweet pickles, and I liked that. So I tried sweet pickles in other stuff . . . and sweet relish is often offered with hot dogs and burgers - so are onions - so I tried them on hot dogs.
Kids . . . .