Boil the pasta: Bring a medium pot of water to a rolling boil and season with a big pinch of kosher salt. Add the pasta and cook to al dente according to the package instructions. Reserve 1 cup of the cooking water just before draining.
Sear the scallops: While the pasta boils, remove the scallops from your refrigerator. Pat them dry and season all over with salt and black pepper. When your pasta is halfway through boiling, heat a large skillet over medium-high. Add 2 tablespoons of the olive oil and, once the oil begins to shimmer, add the scallops. Sear in batches if necessary so as not to crowd the pan. Cook, flipping until golden brown on each side, about 2 minutes per side. Transfer to a rimmed plate and tent loosely with foil to keep warm.
Make the sauce: Leaving the skillet on medium-high, add ⅓ cup of olive oil. When the oil shimmers, add the shallot, garlic, Aleppo pepper and a pinch of salt. Turn the heat to medium-low and cook, stirring frequently until fragrant, 1 to 2 minutes. Stir in the lemon juice and ¼ cup of the pasta cooking water. Add the milk and parmesan and stir until everything comes together, about 1 minute.
Add the pasta to the sauce: Add the drained pasta, lemon zest, and parsley. Toss to coat. The pasta should look nice and glossy. If it’s dry, add a splash more of the pasta cooking water and give it a good stir.
Add the scallops: Add the scallops and any accumulated juices and toss very gently to incorporate. Taste and adjust the seasoning, adding more parmesan, salt, pepper, Aleppo, and lemon juice to your liking. Serve immediately.
Scallops are best served immediately, so it's a good idea to prepare any sides or salads you're serving ahead of time.
If you’re working with a smaller pan, brown the scallops in batches. This will help them get a nice sear. Once you’ve added the parmesan to the sauce, you can scrape everything into the large pot where you boiled the pasta and add the cooked pasta. This will give you plenty of room to stir, rather than trying to force your small pan to work.
Scallops can get dry and rubbery when overcooked. Make sure your pan is ripping hot, and sear for only 2 minutes per side. They should turn golden brown and release easily from the pan, which means they’re ready to flip. If they’re sticking, give them a few more seconds and try again.
Reheating scallops is not recommended as they turn rubbery, so enjoy any leftovers cold or at room temperature.