Pat the steaks dry with paper towel. Arrange the steaks in a single layer on a plate or tray. Drizzle lightly with olive oil and season very generously with salt and pepper. Repeat on other side. You can do this anytime up to a day ahead and cover the steaks and refridgerate until ready to cook. If seasoning the steaks several hours or a day ahead, let the steaks sit on a wire rack over a tray so the excess moisture will drip off instead of pooling and making the meat wet.
Let the steaks sit at room temperature for 30 minutes (or maximum 2 hours) before cooking.
Heat a cast iron skillet over medium heat until very hot. Flick a drop of water in the pan to see if it sizzles, that's how you'll know the pan is ready.
Add the steaks in a single layer. Do not crowd the pan, you may need to cook in batches or use 2 pans if necessary. Allow to sear for 4-5 minutes (4 for medium rare, 5 for medium) without moving the steaks, pressing down on the steaks all over with a spatula now and again to get a nice even sear.
If cooking Strip Loin Steaks, flip the steaks on their sides and sear the fatty strip on the steak for 1-2 minutes.
Sear the steaks on the other side for 2-3 minutes (2 for medium rare, 3 for medium), pressing down all over to get an even sear.
Add the butter and herbs/garlic if using and continue to cook for another 2 minutes, tipping the pan around to distribute the flavours and somewhat "baste" the steaks in the mixture. You can also tip the pan and spoon the butter over the steaks as you go.
Remove the steaks to a plate or cooling rack over a tray and tent with foil. Allow to rest 5 minutes before serving. Pour the pan juices/butter into a dish so they don't scorch with the residual heat from the pan and reserve for spooning over the meat when you serve.