There's apparently something called T Magazine and Rosario Dawson did an interview for it a few weeks back.

In it, she discusses lesbian sex, being completely naked on screen, abortion, and the following sex scene...

That's from Alexander, the Oliver Stone film Dawson addresses in her T Mag interview:

The only sex scene I've done that caused a fuss was the one I did with Colin Farrell in ''Alexander.'' That scene was intense. I thought it was necessary to the movie