Prepare the pasta: Bring a large pot of salted water to a boil. Cook spaghetti according to package directions until al dente, about 9-10 minutes or 1 minute less than package instructions. Reserve 1/2 cup of pasta water before draining.

Prepare the scallops: While pasta cooks, thoroughly pat scallops dry with paper towels. Season lightly with salt and pepper.

Sear the scallops: Heat 2 tablespoons olive oil and 2 tablespoons butter in a large skillet over medium-high heat until butter is melted and mixture is sizzling. Add scallops in a single layer without overcrowding. Sear for 1-2 minutes per side until golden brown and just cooked through. Transfer to a plate and cover to keep warm.

Make the sauce: In the same skillet, add remaining olive oil and butter. Add minced garlic and red pepper flakes (if using), sautéing for 30 seconds until fragrant. Pour in white wine, scraping up any browned bits from the pan, and simmer for 1-2 minutes until slightly reduced.

Create the creamy base: Stir in heavy cream and bring to a gentle simmer. Cook for 3-4 minutes until slightly thickened. Add Parmesan cheese and stir until melted and smooth.

Combine: Add drained pasta to the sauce, tossing to coat. If sauce is too thick, add reserved pasta water a tablespoon at a time until desired consistency is reached.

Finish the dish: Gently fold in the seared scallops, lemon juice, and half the parsley. Season with salt and pepper to taste.

Serve: Transfer to warm plates or a serving dish. Garnish with remaining parsley and lemon zest.