I was always intimidated by cooking sea scallops. All the recipes and discussions I saw online said you had to use the dry or "diver" scallops. They said you'd never get a good sear on frozen and they were only good for soups or stews, etc. I can't afford to buy the dry ones so I bought some lovely frozen ones from Sam's Club. I got a beautiful sear and they were perfectly tender and sweet. I've covered the basics here on how to cook them. Once you learn this you can add all kinds of spices/sauces for added flavor.
There are two critical points here. First, you need a heavy cast iron skillet. I don't know of anything else that will give you the same sear. Second, don't be timid about the preheating, it has to be HOT.
I start defrosting the scallops by placing them on a paper towel lined plate, covering with plastic wrap and placing in the fridge in the morning. About an hour before time to cook, remove them from the fridge. They probably still have their ice coating but are soft to the touch. They're almost defrosted. Rinse the ice off and dry well with paper towels. Place back on fresh towels on the plate and let come to room temp while getting dinner ready.
Place the cast iron skillet on medium high heat for about 15 minutes. No oil yet. When it's screaming hot add the oil and reduce to medium heat.
Salt and pepper the scallops and place in the oil. DO NOT CROWD, I only do 5 at a time. DO NOT try to move them. Let them sit and sear for 2 to 3 minutes. They will begin to release when they are ready to turn. Turn them over and continue to cook approx 2 minutes. The second side will not get as brown. Use tongs to gently squeeze and test that they are still somewhat soft when squeezed. Overcook them and they become rubber.
Remove to a warmed serving plate and cook the rest. Add more oil if needed, but watch your temperature, keep it hot.
After the last ones are cooked, drain any remaining oil. Add the butter and let it brown. This will go quickly. Remove from heat, stir in the grated lemon peel and pour over the scallops.