Begin by thinly slicing the onions, then heat the olive oil in a large skillet over medium heat. Add the onions along with a pinch of salt, and sauté them gently for about 30–40 minutes, stirring frequently until they turn a rich, golden brown.

In a separate saucepan, melt the butter over medium heat. Once melted, whisk in the flour and cook for about 2 minutes until bubbly and light golden. Gradually add the heavy cream while continuously whisking, and let it simmer until thickened, around 5-7 minutes.

Bring a large pot of salted water to a boil and add the cavatappi macaroni. Cook the pasta according to package instructions until it is al dente, typically about 8-10 minutes. Drain the pasta and set it aside.

In the skillet that held the caramelized onions, combine the cooked cavatappi with the creamy béchamel sauce. Mix thoroughly to ensure all pasta is evenly coated.

Preheat your oven to 350°F (175°C). Transfer the pasta mixture into a greased baking dish, spreading it evenly. Top with the remaining caramelized onions and sprinkle a generous amount of crispy breadcrumbs.

Place the baking dish in the preheated oven and bake uncovered for 10-15 minutes, until the breadcrumbs are golden brown and crispy.

Remove the baked pasta from the oven and let it sit for a couple of minutes to set. Serve hot, garnished with freshly chopped parsley.