To assemble salad, wash purslane and trim of any large stems. Tear stems into bite-sized lengths. Meanwhile, husk grilled corn, if needed, and cut kernels off the cob. Toss purslane, corn, and red onion together with a pinch of sea salt in a large salad bowl. Drizzle with dressing, and turn to coat. Drizzle a bit more dressing on top and finish with lots and lots of fresh ground pepper.