Is it safe to eat a dish made with vinegar if the vinegar lid had black stuff on it?

The "black stuff" is most likely mold. I have found it under the lids of many foods I preserved and ate without suffering any adverse health consequences, including various vinegars.

if it's wine vinegar it's completely safe. that's simply a layer of mother of vinegar (mycoderma aceti). If there is still some unfermented sugar in the vinegar it may form even if is a store-bought one. It's a natural process.