Begin by thinly slicing your onions and heating a large skillet over medium heat. Add a generous drizzle of olive oil, then toss in the sliced onions. Cook for 30-40 minutes, stirring occasionally, until they become golden brown and caramelized. For added sweetness, sprinkle in a teaspoon of sugar halfway through the cooking process.

Once the onions are caramelized to perfection, move them to the side of the skillet. In the same pan, melt a couple of tablespoons of butter over medium heat. Whisk in flour and gradually add heavy cream, stirring constantly until the mixture thickens and bubbles gently. Mix in about two-thirds of the caramelized onions along with salt, pepper, and fresh parsley.

In a large pot, bring salted water to a boil. Add your cavatappi macaroni, cooking it until just shy of al dente, usually about 2 minutes less than package instructions. This step is crucial as the pasta will continue to cook while baking. Drain and set aside, allowing the pasta to cool slightly.

Transfer the cooked pasta into the skillet with the béchamel sauce, ensuring the pasta is evenly coated with the creamy mixture. Gently fold in the remaining caramelized onions.

Preheat your oven to 350°F (175°C). Now, transfer the pasta mixture into a greased baking dish, spreading it out evenly. Top it generously with the remaining caramelized onions and a layer of crispy homemade breadcrumbs.

Bake the assembled dish in the preheated oven for 10-15 minutes, or until the breadcrumbs are golden and crisp. Once ready, remove from the oven and let it rest for a few minutes before serving.