Tough greens, like kale and collard greens, can take some work to make them suitable for salad but if you marinate them in oil for a bit first, you’ll tenderize them, make your salad even tastier, and start a light dressing all at the same time.
Source: LifeHacker – Marinate Tough Greens in Oil (and Use It for Dressing) for Tastier Salads