I accidentally added one cup of dry red wine to my French onion soup instead of only 1/2 a cup. Will my soup be ruined?

Cognac definitely adds something. I typically use white wine in onion soup, and - if I have some around - will also add a bit of Madiera or sherry (even Marsala) - there's something about that rich flavor that really compliments the caramelized onions, especially with the gruyere on top.

I like the gruyere also but I don't use that big thick gloppy slab. What I prefer is to grate the gruyere over the croutons, lined up on a sheet pan and then I hit that with a blow torch. No blow torch? The broiler works. Then float them on top of each portion.

Thank you so much! I did add a cup after I a overpoured the wine which is why it's now at 7 cups of broth. It was originally 6.

I agree with amysarah. Should be no problem. I'd worry more about your onions which need to cook down for about 45 minutes under your watchful eye. Too much wine? Not a problem.

Oh 7 cups of a mixture of beef broth and reduced sodium beef broth.