Where can I sell domain names and earn in bitcoins?
There are no sites that automatically buy domains at all that I know of. Most of the domain marketplaces don't accept Bitcoin, but the ones that do don't have much traffic.

I use bitcointalk. Just go into their Digital goods section, make a topic called [WTS] INSERT DOMAIN, and in the message, put in the domain registrar, how much you want for it, when it will expire, etc.

If you want, you can host an auction.

Id recommend 100% to use escrow. Here's a list of the best escrows on the forum. https://bitcointalk.org/index.php?topic=855778.0