I first glimpsed a version of these cookies on foodgawker, posted by Jamie (aka Sophistimom). There's nothing I love more than a simple shortbread cookie, especially one bursting with citrus flavor.
I tweaked the original recipe a bit and made them gluten-free by replacing the all-purpose flour with superfine brown rice flour. It worked like a dream. The finished cookies were delicious and you can't even tell the difference. The crumb is tight and crisp, just how a shortbread should be. I gave samples to two gluten-free friends and both gave the thumbs up.