Preparation Bring vinegar, oil, sugar, and 1/4 teaspoon salt to a simmer in a small saucepan. Stir in shallots and remove from heat. Bring water to a simmer in a large pot, then add kale, 1/2 teaspoon salt, and 1/4 teaspoon pepper and cook, uncovered, stirring, until kale is wilted and crisp-tender and liquid has evaporated, 5 to 8 minutes. Toss with shallot mixture, then season with salt and pepper.
Preparation Bring vinegar, oil, sugar, and 1/4 teaspoon salt to a simmer in a small saucepan. Stir in shallots and remove from heat. Bring water to a simmer in a large pot, then add kale, 1/2 teaspoon salt, and 1/4 teaspoon pepper and cook, uncovered, stirring, until kale is wilted and crisp-tender and liquid has evaporated, 5 to 8 minutes. Toss with shallot mixture, then season with salt and pepper.