Ingredients for Beef Fajita Recipe: 1 pound sirloin steak (flank steak, tenderized round steak, skirt steak) 1 onion, sliced. 1 red and / or green Bell pepper, sliced (optional) 1 tablespoon olive oil or vegetable oil. 1 teaspoon lite soy sauce. 2 tablespoons water. 1/2 teaspoon fresh lime juice.