Preheat your oven to 135c/275f. Wash your kale, dry it out on some kitchen paper and cut off any stalks - so you're just left with the tender leaves. Place the kale into a large bowl and drizzle the oil over the top. Gently massage the oil into all of the leaves with your hands. One tbsp doesn't seem a lot, but it will stretch to cover all the leaves. Divide the kale between two metal baking trays (in a single layer) and place in the oven for 15 minutes.
Take your kale out of the oven. It will have shrunk down significantly. Place in your serving bowl and sprinkle on the salt and caster sugar. Toss the kale gently, then sprinkle the confectioners sugar on top before serving.