Begin by slicing your large yellow onion into thin, even slices. In a skillet, heat 2 tablespoons of olive oil over medium heat. Add the sliced onions and sauté for about 25-30 minutes, stirring occasionally until they turn golden brown and caramelized, adding minced garlic during the last 5 minutes.

For the chili oil, heat 3 tablespoons of olive oil in a small saucepan over medium-low heat. Add a sliced garlic clove, 1 tablespoon of red chili flakes, and 1 teaspoon of paprika. Stir for 2-3 minutes until fragrant, then stir in 1 teaspoon of soy sauce and simmer for an additional 2 minutes before removing from heat.

In a large pot, bring salted water to a boil. Cook 12 oz of pasta according to package instructions until al dente, usually about 8-10 minutes. Reserve 1 cup of pasta water before draining, then set the cooked pasta aside.

Return the drained pasta to the pot and add the caramelized onions along with their oil. Drizzle the homemade chili oil over the pasta and toss to combine, adding reserved pasta water if needed for desired consistency.

Serve the pasta hot in bowls, topped with grated Parmesan cheese and fresh herbs. Add extra chili flakes for more heat if desired.