Step 1

In a large Dutch oven, bring 4 quarts water to a boil. Stir in the pasta and 1 tablespoon salt, then cook, stirring occasionally, until just shy of al dente. Working quickly, remove about 2 cups of the cooking water, then stir the kale into the pot and cook for another 1 minute. Drain and set the pasta-kale mixture aside.

Step 2

In the same pot over medium, combine the oil, fennel seeds, pepper flakes and rosemary. Cook, stirring constantly, until fragrant and sizzling, 1 to 2 minutes. Add the tomato paste and ½ teaspoon each salt and black pepper, then cook, stirring often, until the paste browns and slightly sticks to the pot, 2 to 3 minutes.

Step 3

Add 1½ cups of the reserved pasta water and bring to a simmer, scraping up any browned bits and stirring to dissolve the tomato paste. Add the pasta-kale mixture and cook, stirring, until the pasta is al dente and has absorbed the excess liquid, about 2 minutes; add more reserved water as needed so the pasta is silky and lightly sauced.

Step 4

Off heat, stir in the cheese, then let stand for 1 to 2 minutes to allow the cheese to melt. Taste and season with salt and black pepper. Serve drizzled with additional oil and sprinkled with additional pepper flakes.