If a onion has black dots on it is it rotten?!
Answers: Yes. Those black dots are spots of mold.
Cut into it. Probably not
yes. its mold. so dont eat it.
If the black dots rub off its just mold, and you can just wash it and/or cut off those parts and it will still be fine to use.
Onions are layered... just peel off the outer layer and use the rest.