Pour in heavy cream, simmer for 2-3 minutes, then add Parmesan cheese, stirring until melted and sauce is creamy. Adjust with reserved pasta water if needed.
Toss cooked linguine into the sauce, add lemon juice, and season to taste. Cook for 1-2 minutes, then garnish with parsley and red pepper flakes if using.
Notes
For extra flavor, sprinkle additional Parmesan or fresh herbs before serving.