Bring a large pot of salted water to a boil and cook the penne pasta until just al dente, about 10 minutes. Drain and set aside.
While pasta cooks, peel and devein the shrimp if not already done. Thinly slice the garlic cloves and zest and juice the lemon, keeping the zest and juice separate. Chop the parsley finely.
Heat a large skillet over medium-high heat. Add olive oil and a tablespoon of butter, letting the butter melt and foam. When fragrant and bubbling, add the sliced garlic. Cook until golden and fragrant, about 30 seconds.
Add the shrimp in a single layer. Cook for 2-3 minutes until they turn pink and opaque, then flip and cook another 1-2 minutes until just cooked through with slight char on the edges. Remove shrimp from the pan and set aside.
Sprinkle red pepper flakes into the skillet if using. Add the lemon zest and juice, stirring to coat the garlic and shrimp remnants. Let the mixture bubble gently for about a minute to meld the flavors.
Return the cooked penne to the skillet and toss to coat in the lemon-garlic sauce. Cook together for 1-2 minutes, allowing the pasta to absorb some of the flavors and become glossy.
Return the sautéed shrimp to the skillet, tossing gently to combine. Taste and season with salt and freshly ground black pepper as needed.
Sprinkle chopped parsley over the dish for a fresh, herbal finish. Give everything a final toss to distribute the herbs evenly.
Serve immediately with extra lemon wedges if desired, enjoying the bright aroma and tender shrimp coated in flavorful sauce.
