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

In a skillet, heat 2 tablespoons of olive oil over medium heat. Add minced garlic and sauté for 1 minute until fragrant.

Add the shrimp to the skillet, season with salt, pepper, and red pepper flakes (if using). Cook for 2-3 minutes on each side until shrimp are pink and opaque.

Add the cooked spaghetti to the skillet with the shrimp. Pour in lemon juice and zest, and toss everything together. Drizzle with remaining olive oil and sprinkle with parsley.

Serve immediately, garnished with additional parsley if desired.