Thanks again to BK Swappers, I had a delicious jar of (labor intensive) watermelon jam. It has all the flavor of watermelon and the perfect texture for jelly. I'm still shocked that something so ethereal in texture could yield jam! Borrowing Kicinski's recipe for thumbprints, I made a simple dough to match the flavor. Unfortunately I forgot to add my xanthum gum, so these cookies turn into a jam cookie paste soon as you get them to your mouth (and that's if they don't crumble on their way!) Hopefully this is a lesson I only need to learn once.