Add sausage to skillet and cook for 2 minutes over medium heat. Add chopped onion, red pepper flakes and minced garlic, stir. Continue cooking and breaking up the sausage.
Meanwhile, begin boiling noodles. Drain and rinse with cold water when al dente, set aside.
Add undrained can of diced tomatoes, salt and pepper to meat mixture and stir. Taste and adjust salt and/or pepper.
Begin adding kale, a large handful at a time, folding in with a large spoon. This seems like A LOT of kale, but trust me, it will cook down!! Continue adding kale and stirring until fully incorporated.
Simmer for a few minutes and let this all "get married" as we say in our Kitchen, stirring occasionally. Depending on your stove top, you may need to adjust the heat to low/simmer.
Add noodles, and stir until everything is mixed together. Serve with grated or shredded Parmesan on top...enjoy!