Heat 3 tablespoons of olive oil in a large skillet over medium-low heat. Add 2 large sliced onions and a pinch of salt. Cook for about 20–25 minutes until golden brown.

While onions are caramelizing, boil a large pot of salted water. Cook 8 ounces of fettuccine until al dente, usually around 8–10 minutes. Reserve ½ cup of pasta water before draining.

Combine the drained fettuccine with the caramelized onions in the skillet, tossing to coat. Add reserved pasta water gradually if needed for desired sauce consistency.

Season with newly ground black pepper and additional salt. Serve topped with grated Parmesan cheese and chopped fresh parsley.