On Monday, Uma Thurman promoted the new BMW i8 "Born Electric" Spyder concept vehicle at Avenue of the Americas in New York City. But what got people's attention was the enormous diamond ring on her left hand.

The actress gave birth to her third child, daughter Rosalind Arusha Arkadina Altalune Florence Thurman-Busson,  in July. It was her first baby with businessman boyfriend Arpad Busson. Or should we say, fiance?

Last month Uma joined the cast of Lars Von Trier's upcoming erotic drama, Nymphomaniac. The film will reportedly feature unsimulated sex scenes from some of its stars, which include Shia LaBeouf, Charlotte Gainsbourg, Stellan Skarsgard, Jamie Bell, Willem Dafoe and Connie Nielsen.

Check out more photos of Uma and her ring...