01 - Boil fettuccine in salted water until al dente. Reserve 1/2 cup pasta water before draining.
02 - Heat olive oil and butter in skillet over medium heat. Add onions and salt. Cook 10 minutes until softened and lightly browned.
03 - Sprinkle brown sugar over onions. Continue cooking 15-20 minutes, stirring frequently, until deeply golden and caramelized.
04 - Stir in minced garlic and chopped red chili. Sauté 1-2 minutes until fragrant.
05 - Add honey, heavy cream, Parmesan, red pepper flakes, and black pepper. Simmer 2-3 minutes until slightly thickened.
06 - Add cooked pasta to skillet. Toss thoroughly, adding reserved pasta water one tablespoon at a time until sauce coats pasta evenly.
07 - Adjust seasoning to taste. Serve immediately topped with fresh parsley and additional Parmesan.