Hint for perfectly cooked scallops

One of the keys to perfect scallops is ensuring they are completely dry before searing. Pat them with paper towels and let them sit uncovered in the refrigerator for 30 minutes if possible. 

Use a very hot pan with neutral oil, and resist the urge to move them. You should hear an aggressive sizzle immediately - if not, the pan isn't hot enough. 

Professional chefs consistently sear scallops on both sides - typically 1½-3 minutes per side depending on size, creating a golden crust on each side while keeping the center translucent.

Cast iron pans have high heat capacity, which means they can hold a lot of heat energy. When you place cold scallops into any pan, it's going to start removing heat out of the pan at an incredible rate. You need high heat capacity in the pan to replace what's already gone into the cold scallop to keep the sear moving forward. Cast iron does this most efficiently. HOWEVER, cast iron also retains heat, so once seared to perfection, make sure to quickly remove the scallops to stop them from continuing to cook.