Scale back the warmth to medium. Add the purple onion and cook dinner, stirring sometimes, till softened and flippantly caramelized, 6 to eight minutes. Add the kale just a few handfuls at a time, stirring after every addition in order that it begins to wilt, till all the kale is added, about 1 minute complete. Add 1/4 teaspoon kosher salt and 1/4 teaspoon black pepper and stir to mix.
