Boil pasta in salted water until al dente. Reserve ½ cup pasta water and drain.
In a skillet, melt 2 tbsp butter and sear shrimp 2 minutes per side. Remove.
Melt remaining butter, sauté garlic and pepper flakes. Add lemon juice and cream.
Stir in reserved pasta water and parmesan until smooth.
Toss in cooked pasta and return shrimp. Stir gently to combine.
Garnish with parsley and serve hot.
