Bring a large pot of salted water to a boil. Prepare the pasta according to the package instructions, cooking until al dente. Reserve 1 cup of the pasta cooking water before draining the pasta.

Heat the olive oil in a large skillet over medium heat. Add the garlic and red pepper flakes. Stir and cook for 30 seconds to 1 minute, or until the garlic is lightly browned around the edges. Add the kale, salt, and several grinds of pepper and cook, tossing with tongs, until the kale is wilted, up to 1 minute.

Add the spaghetti and toss to combine. Add 1/2 cup pasta water and the lemon juice and zest and toss. If the pasta is seeming too dry, add the remaining 1/2 cup pasta water to create a light sauce.

Season to taste. Garnish with parsley and serve with Parmesan or vegan Parmesan.