I finally found the perfect fabric for them! The day it arrived I was so excited that I refused to go to bed before it was done. It took me less than hour to actually sew it. I used the old valance as a measurement guide and double folded the edges in using 1/2 inch. This was so simple. So very simple.
I played around with the idea to make two vertical panels, but the space between the window and the start of the (ugly) cabinets isn't big enough and would just look weird.
The old curtains were maroon and the desert sun really killed them. They're nearly white in spots on the back in the shape of the blinds. Here's the before: