Bring a large pot of generously salted water to a boil. Cook the spaghetti or linguine until al dente according to the package directions, then reserve at least 1/2 cup of pasta water before draining.

Pat the shrimp dry and season with about 1/2 teaspoon kosher salt and the black pepper. Heat the olive oil and 1 tablespoon butter in a large skillet over medium-high heat, then cook the shrimp in a single layer for about 1–2 minutes per side, just until pink and opaque.

Transfer the shrimp to a plate as soon as they are cooked. Reduce the skillet heat to medium and add the remaining 3 tablespoons butter, garlic, and optional red pepper flakes, cooking for 30–60 seconds until fragrant but not browned.

Pour in the dry white wine or low-sodium chicken broth and simmer for 2–3 minutes. Scrape up any browned bits from the bottom of the skillet so they become part of the sauce.

Add the drained pasta and fresh lemon juice to the skillet. Toss well, adding the reserved pasta water a few tablespoons at a time until the butter sauce lightly coats the noodles.

Return the shrimp to the skillet and toss gently just until heated through. Stir in the optional Parmesan cheese and adjust the consistency with another small splash of pasta water if needed.

Garnish the pasta with chopped fresh parsley and serve immediately. Pass lemon wedges at the table for an extra fresh, tangy finish.