Bring a large pot of salted water to a boil and cook pasta according to package instructions until al dente.
While pasta cooks, pat shrimp dry and season with salt and pepper.
In a large skillet, heat olive oil and 2 tablespoons of butter over medium-high heat.
Add shrimp to the skillet and sear for 1.5 to 2 minutes per side until just opaque; remove shrimp from skillet and set aside.
Reduce heat to medium and add the remaining 2 tablespoons of butter to the same skillet.
Add minced garlic and red pepper flakes, sautéing for 60 seconds until fragrant.
Pour in heavy cream and simmer for 2 to 3 minutes until slightly thickened.
Whisk in the grated Parmesan cheese until melted and the sauce is smooth.
Reserve 1/4 cup of pasta water, then drain the pasta.
Add the pasta, cooked shrimp, lemon juice, and reserved pasta water to the skillet.
Toss thoroughly to coat the pasta in the sauce, garnish with parsley, and serve immediately.