Cook pasta in a large pot of salted water, until about 2 minutes before tender. *Reserve 3 cups of pasta cooking water.* Don’t forget to do this! Then drain pasta.
Melt 3 tablespoons butter in a nonstick skillet over medium heat. Add kale, red pepper flakes, and 1 grated garlic clove and cook, swirling pan, until kale is slightly wilted. Stir in 3/4 cup pasta cooking water. Cook until kale is very soft and wilted, another 2 minutes or so.
Reduce heat to low and toss in the al dente pasta and remaining butter. Stir in the Parmesan and 1/2 cup pasta cooking water. Toss until the cheese is melted and a thick sauce coats the pasta. Add more pasta water if things don’t seem saucy enough, you want a glossy sauce to coat all of the noodles. Stir in the juice of the lemon, reserving the zest for the breadcrumbs. Taste the pasta, and add the juice of the second lemon if you want it more lemon-y!
To make the Crispy Parmesan Breadcrumbs: Warm the oil in a nonstick skillet over medium heat. Add the breadcrumbs, garlic, and lemon zest and stir for 3 to 4 minutes, until golden brown. Stir in the Parmesan and stir constantly for 1 to 2 minutes, until the cheese is crispy and coating the breadcrumbs. Season with salt and set aside.
Divide pasta between 4 bowls and top with Crispy Parmesan Breadcrumbs.