Are these correct in American English?

Yes, these are odd questions but correctly said:
Who eats cupcakes? Who writes books?

If you want to use "does," you should name the actor.
Does Jack eat cupcakes? Does anyone eat cupcakes?

I hope this helps.

Thanks

You seem That you don't like cupcakes.

Yes, It is very helpful Thanks

bassaIt is incorrect to say "Who does eat cupcakes?", right?

In most cases it is incorrect. But there is a way you can use it, and it's like this:

-- Does Susan eat cupcakes?
-- No.
-- Does Larry eat cupcakes?
-- No.
-- Does Steve eat cupcakes?
-- No.
-- Does Laura eat cupcakes?
-- No.
-- Well! Who does

bassaYou seem That It seems that you don't like cupcakes.

No. It's not what you think. It's the other people who don't like them. I'm trying to give them away but nobody wants one.

I would take some

Here you go!

Enjoy!

CJ

Yumeeeeeeeeeeeeeeeeee!