Shawarma spiced skirt steak salad

Name: Shawarma spiced skirt steak salad
Cuisine: Middle Eastern
Ingredients: 1/2 cup olive oil; 6 garlic cloves; 1 tsp lemon zest; 1 tsp ground coriander; 1 tsp ground cumin; 1/2 tsp cayenne; 1 tsp salt; 1/2 tsp ground pepper; 1/2 tsp onion powder; 1 1/2 lbs boneless skirt steak or flap steak; 1 yellow onion; Lemon juice; 1 tsp Dijon mustard; 9oz package romaine lettuce; Cherry tomatoes; 1/2 cup crumbled feta; 1/2 small red onion; Pita chips