In a large pot, bring salted water to a boil. Add spaghetti and cook according to package instructions until al dente. Drain and set aside.

In a skillet, melt 2 tablespoons of butter over medium heat. Add minced garlic and red pepper flakes, sauté for about 1 minute until fragrant.

Add shrimp to the skillet, season with salt and pepper, and cook for 2-3 minutes on each side until pink and cooked through. Remove shrimp from skillet and set aside.

In the same skillet, add the remaining 2 tablespoons of butter and lemon juice. Stir to combine.

Add the cooked pasta and shrimp back to the skillet, tossing to coat in the garlic butter sauce. Stir in chopped parsley.

Serve immediately, garnished with additional parsley if desired.