Peel and devein the shrimp. If they are frozen and you don't want to wait for them to thaw out in a bowl of water you can defrost them in the microwave. I've done it lots of times and it works out just fine. The shrimp will thaw real quick in the microwave and will be peelable in just a minute or so.
Put a skillet on at just little hotter than medium and add one tablespoon of extra virgin olive oil. Slice up the lemon and add the slices to the skillet all laying flat. Sprinkle with a little salt and black pepper.
When they are seared turn them over and sear the other side. While all this is happening chop up the garlic. When the lemon slices are seared on both sides add the garlic. Immediately put a tablespoon of butter on the garlic. I was enjoying my first glass of Chianti (are you surprised?) so I added a little to the pan.
Bring it to a simmer and add the shrimp laying them out on their sides. When they get pink turn them over and cook the other sides. The wine will reduce a little as the shrimp cook and you will be ready to serve up your Garlic Shrimp with Seared Lemon Slices.