01 - Heat olive oil in a large deep skillet or Dutch oven over medium heat. Add onion and cook for 3 to 4 minutes, stirring occasionally, until softened.
02 - Add minced garlic and cook for 1 minute, stirring constantly, until fragrant but not browned.
03 - Add dry pasta, vegetable broth, lemon zest, salt, and black pepper. Stir well and bring the mixture to a gentle boil.
04 - Reduce heat to low. Simmer uncovered, stirring occasionally, for 10 to 12 minutes until pasta is al dente and most liquid is absorbed.
05 - Stir in heavy cream, lemon juice, Parmesan cheese, and red pepper flakes if desired. Cook for 2 to 3 minutes until sauce thickens and coats pasta.
06 - Remove from heat. Fold in fresh parsley and adjust seasoning with additional salt, pepper, or lemon juice if needed.
07 - Dish hot, garnished with extra Parmesan and chopped parsley.