Got the recipe from here
1 tsp extra-virgin olive oil
1 tsp (packed) lemon zest
scant 1/8 tsp sea salt
How to make them: Preheat oven to 300°F. On a lined baking sheet, space out 1 cup packed, dry kale leaves (stems discarded). Drizzle with oil, sprinkle with seasonings, and massage into leaves.
On the top or middle rack, bake for 20 minutes, until crisp, rotating the pan and switching racks (top to middle or vice versa) halfway through baking time. Makes 1 or 2 servings.