This pasta dish is bright, thanks to lemon zest, has a touch of heat from red pepper flakes, and is tied together with rich and creamy ricotta. Parmesan softens and gets trapped in the kale leaves, reminding us a bit of creamed kale. You can substitute spaghetti for bucatini, but we really love the way the hollow tubes soak up olive oil and extra flavor. Some quick tips: run your fingers along both sides of the kale to remove the leaves from the stems quickly, and be sure to watch the pine nuts closely because they can burn quickly.