Wash the kale and pull or cut out any stems or ribs thicker than a pencil. Tear the leaves into bite-size pieces and put them in a bowl. Sprinkle with ½teaspoon salt and use your hand to massage it into the kale. Add the lemon zest and juice, finely grate in the garlic, if using, and add the crushed red pepper and oil. Toss to combine, cover, and refrigerate until evening.