How do I remove a black ring on a wooden cabinet top?

Lay a towel over the spot and iron the towel. Medium heat and repeat until it's gone.

I watched this video to be sure it answered your question. Once you get past the ad (you can click through after 3 sec.) wait for step 5. That's where you'll find out how to remove the black ring:

https://www.youtube.com/watch?v=TGjyPv4UMGw

Had this happen on an oak end table. I used a sponge with a little chlorine bleach and just laid it on the spill I had for the better part of a day. It worked and all I had to do was touch it up with a little stain and a sealer. Hope it works for you!

rub any oily substance in a circular motion with a micro fiber cloth