Tenderize your flank steak.
Cook the pepper, onion, and garlic in a pan until soft.
Lay down a layer of uncooked spinach on the steak.
Layer the cheese on top of the spinach.
Layer the cooked pepper/onion mixture on top of the cheese
Roll the steak (on the long edge).
Place (pre soaked) skewer sticks about half an inch apart all the way down the roll.
Cut the roll into pieces so that each piece has a skewer holding it together.
Sear in a pan with oil or butter until the outside is brown. Do this on both sides.
Place in the oven at 375F and bake until desired doneness.