Bring 4 quarts of generously salted water to a boil. (Less water = more starchy water, and will help create a thicker sauce later on!), cook the pasta until just under al dente, as it will continue to cook a bit in the sauce later on. Reserve 1 cup pasta water, then drain.

Meanwhile, heat the olive oil in a large saute pan over medium-high heat. Pat the scallops dry, season with salt, and add to the pot flat side down. Sear undisturbed for 2-3 minutes, then flip and sear the other side, 2-3 minutes, until just opaque throughout. Transfer to a plate and set aside.

Then, reduce heat to medium and melt the butter in the saute pan. Add the lemon zest, red pepper, and garlic and cook while stirring for 1-2 mins, scraping any browned bits from the pan to incorporate them.

Add the spaghetti and 1/2 cup pasta water to the pan. Increase the heat to medium high, and cook until a slightly thickened, glossy sauce is formed.

Add the cheese and toss, stirring until melty and emulsified, adding more of the pasta water if needed. Incorporate lemon juice (1 tbsp or more) to taste. Season with salt and pepper.

Serve topped with more lemon zest and parmesan cheese shavings.