1. Combine first 3 ingredients in a large zip-top plastic bag; add steak to bag. Marinate 3 minutes, turning once. Remove steak from bag; discard marinade. Sprinkle steak with 1/4 teaspoon salt. Heat a large skillet over medium-high heat. Add butter and oil. Add steak; cook 5 minutes on each side or until desired doneness. Let stand 2 minutes. Cut steak across grain into thin slices.
2. Return pan to heat. Add juice, garlic, and spinach; sauté 1 minute. Remove from heat; add remaining salt.
3. Spoon 2 tablespoons spinach mixture into each pita half. Place 1 tablespoon onion, 3 cucumber slices, and 1 1/2 ounces steak in each pita half; sprinkle 1 tablespoon cheese in each pita half.
Creamy hummus: Combine 1 cup rinsed and drained canned chickpeas, 2 tablespoons lemon juice, 1 tablespoon tahini (roasted sesame seed paste), 1/4 teaspoon salt, and 1/8 teaspoon ground red pepper in a food processor; process until well blended. Gradually add 3 tablespoons extra-virgin olive oil; process until smooth. Serve with red pepper slices and baby carrots.