Bring a large pot of lightly salted water to a boil; add spaghetti and cook, stirring occasionally, until tender yet firm to the bite, about 10 minutes or 1 minute less than directed on the package.

Meanwhile, heat oil in a large skillet over high heat. When oil just starts to smoke, add scallops and move them into a single layer. Let sear on high for about 1 minute. Toss to turn.

Add butter and stir scallops until butter melts. Stir in garlic.

Add lemon zest and red pepper flakes. Stir in sherry and cook and stir until alcohol cooks off, about 1 minute.

Pour in cream. When mixture begins to simmer, reduce heat to medium-low. Add salt, pepper, and lemon juice.

Drain pasta. Transfer to skillet with scallops; bring to a simmer. Add 1/2 of the chopped parsley. Cook until pasta is heated through and tender, about 1 minute.