Slowly rotate while using Quaternion.FromToRotation

In my 2d game I am seemingly forced to use FromToRotation to keep things rotating on the correct plane, problem is is that FromToRotation jumps immediately from current to end and I want to slowly rotate.

I have:

Player
Enemy who tracks the player and rotates to face him.

What are my options for rotating the enemy slowly to face the player while using Quaternion.FromToRotation? I’ve tried Lerp but I couldn’t get it work. If any more details are needed I’ll be glad to add.

http://forum.unity3d.com/threads/making-an-object-rotate-to-face-another.1211/