Rinse kale, drain, remove stems and rough chop, set aside.
Cook pasta according to package directions. Drain, set aside.
While the pasta cooks, Heat the oil in a large pot over medium heat. Add the kale, garlic, onion, 1/2 tsp salt, and 1/4 tsp pepper. Cook covered, stirring occasionally, until kale has wilted, about 6 minutes.
Add the drained pasta to the kale and toss, allow to cool 5 minutes.
Add the Parmesan and red pepper flakes. Toss to combine, add salt and pepper to taste.