Heat two tablespoons of the olive oil over medium-high heat in a medium saucepan and add the onion. Sauté until the onion is tender and lightly browned, about 4 minutes. Add the couscous and stir until the couscous begins to turn golden and smell toasty, about 4 to 5 minutes. Add the 4 cups water and salt to taste and bring to a boil. Reduce the heat, cover, and simmer for about 15 minutes, or until the couscous is tender and the liquid is absorbed. Line a rimmed baking sheet with aluminum foil, spray it with nonstick cooking spray (or a brush of oil), and spread the couscous out on the baking sheet to cool to room temperature.
Meanwhile, roughly chop the kale. Rinse well in a colander, then shake the colander to get rid of excess moisture. Heat a large pot over medium-high heat. Add 1 more tablespoon of olive oil, then add the shallots and sauté for 4 minutes. Add the garlic and stir for another minute. Add the kale, season with salt and pepper, and sauté for about 5 minutes, until the kale is wilted (if you like it softer, cook it a bit longer).
In a large bowl, combine the remaining tablespoon of olive oil, the jalapeño, lemon juice, red onion, and salt and pepper, then transfer the cooled couscous to the bowl and toss to combine and coat the grains. The grains may have clumped up a bit — tossing them with the dressing should separate them. Toss in the sautéed kale, taste, and adjust the seasonings as needed. Serve slightly warm or at room temperature.
Notes
Check the couscous package directions, as different brands may have different advice about amounts of liquid, and time (the size of the pasta may also vary), and adapt these directions to include what your package says.