Complete blender nub here, just started using it. I was playing around with a NURBS circle, trying to make a simple plate. All I did was duplicate the circle a few times with shift + d and scaled it each time, then joined the faces with F, and got this:



How can I close up that empty spot in the center where the I originally put the NURBS circle? I figure it should be pretty simple, but I couldn't figure it out myself.