Light a grill. Place a 10-inch springform ring (not the bottom) on the grill to contain the kale. Carefully pat the kale inside the ring, pressing down to form an even layer. Grill until lightly charred on the bottom, 3 minutes. With tongs, turn the kale over and grill on the other side for 3 minutes. Alternatively, grill the kale on a perforated grill pan, tossing occasionally.