Olive oil, salt and pepper top round and grill to your liking. I like mine med rare, especially for this.
While grilling steak in food processor combine yogurt, feta, lemmon, hot sauce,garlic,oregano, cumin,coriander, salt and pepper. process and set aside, this is your tzatziki sauce (reserve half for greek chicken roulade)
Let steak rest for 10 min. Preheat oven to 450. slice up onion, tomato and olives. Slice steak on bias then cut into bite size pieces.
prepare baking sheet with foil. spread pita pockets with tzatziki sauce layer spinach, steak, olives, onion tomato and then cover each with two slices of Mozzerella cheese (like a pizza). place on baking sheet.
bake for 10 min at 450 degrees. Easiest sliced with pizza wheel after cooled a bit.