Boil salted water, cook fettuccine until al dente (9–11 mins), drain, and set aside.
Melt butter and olive oil in a skillet over medium heat. Add garlic; cook 1–2 mins until fragrant.
Add cream, bring to a simmer. Stir in Parmesan gradually until melted and thickened, about 3–4 mins.
Add salt, pepper, and optional red pepper flakes.
Stir in chopped lobster and lemon juice. Warm for 1–2 mins, don’t overcook.
Add pasta to the sauce and toss to coat.
Serve with parsley and extra Parmesan if desired.