Lay flank steak out flat, trim any extra fat or silver skin. 

Generously season steak with salt and pepper. 

Add olive oil, herbs, lemon zest and juice, and diced garlic to a large bowl or (preferably) a large plastic bag and mix well. 

Add steak to bag and let marinate for 40 minutes up to two hours. 

Preheat oven to 500 degrees (or 450 - as high as your oven broiler can go.)

Add large cast iron pan or skillet to oven. If you don't have a pan or cast iron griddle large enough for your steak, you can use a heavy baking sheet lined with foil. (Cast iron will get best results, but don't worry if you don't have it.) Make sure pan is close to broiler, but not touching (I give about 5" to make sure my steak has room under the broiler since I have a gas flame broiler and don't want to start a fire from spattering fat.) Let pan get scorching hot before adding steak to it for the best texture.

Remove steak from bag, and sprinkle with garlic powder. 

Cook steak in oven for 8 minutes, then flip to other side and cook another 8.

Continue to cook until steak has reached desired doneness: 125 degrees with a digital thermometer inserted into the fattest part of the steak will give you a rare steak. 135 degrees will get you medium rare, 155 for medium well, and 165 degrees for well done.

When your steak is done to your taste, remove from oven.

Place a small piece of foil over the steak to "tent" it and let it finish carryover cooking as it rests for 10 minutes. 

When steak has rested for at least 10 minutes (don't rush - if you cut it right off the grill the steaks juices will all run out), slice it width-wise (so you have lots of thin strips instead of just a few long strips) against the grain - which is essential to keeping the steak from being too chewy or tough. 

Serve immediately and enjoy!