Bring a large pot of salted water to a boil. Add penne pasta and cook according to package instructions until al dente. Drain, reserving ½ cup of pasta water.

Pat the shrimp dry with paper towels and season with salt and pepper.

Melt unsalted butter in a skillet over medium heat, add minced garlic and red pepper flakes; sauté for 1-2 minutes until fragrant.

Add seasoned shrimp in a single layer, cooking for 2-3 minutes on each side until pink and opaque.

Reduce heat and add the drained penne, reserved pasta water, and fresh lemon juice; toss to combine.

Sprinkle with parsley and adjust seasoning before serving hot, topped with grated Parmesan.