1. Bring a large pot of salted water to a boil. Cook the pasta according to package instructions until al dente. Reserve 1 cup of pasta water before draining.
2. While the pasta cooks, heat 2 tablespoons of olive oil in a large skillet over medium-low heat. Add the sliced onions, sprinkle with 1 teaspoon salt and 1 teaspoon sugar, and stir to coat.
3. Cook the onions gently, stirring occasionally, for about 30-40 minutes. You’re aiming for soft, deeply golden, and sweetly caramelized onions. Patience is key here—this slow cooking unlocks all the flavor.
4. Once the onions are almost done, stir in the minced garlic and cook for another 2 minutes until fragrant.
5. In a small pan, warm the remaining 1 tablespoon olive oil with red chili flakes over low heat for 2-3 minutes to infuse the oil. Be careful not to burn the flakes.
6. Add the drained pasta to the skillet with caramelized onions. Toss gently to combine, adding reserved pasta water a few tablespoons at a time to create a silky sauce that clings to every strand.
7. Drizzle the chilli oil over the pasta, season with freshly ground black pepper, and toss once more to distribute the heat evenly.
8. Serve immediately, topped with grated Parmesan and a sprinkle of fresh parsley.

My personal tip: When I first made this recipe, I was so eager to rush the onions that I missed out on that beautiful caramelized flavor. Now, I remind myself (and my kids when they help) that the slow cook is where the magic happens. It’s a simple act of love, really.