So I recently posted a recipe for Quinoa Salad with Apples, Dried Cranberries, Walnuts, and Gouda, and I made it again tonight with a slight variation.
Instead of the arugula, which I didn't even use the first time I made it, I used kale. I chopped up one bunch of kale and added to the skillet with the chopped onions after they had begun to soften and turn light brown. Once the kale wilted, I continued the recipe as usual, adding balsamic vinegar and allowing it to evaporate before removing the mixture from the heat.
I absolutely love kale, so this addition worked really well for me. You could probably achieve similar results by doing the same thing with spinach, although be prepared for the distinct flavor that cooked spinach brings to the party.