Whisk olive oil, red wine vinegar, balsamic vinegar, lemon juice, garlic, basil, oregano, salt and pepper in a bowl until combined. Add flank steak to a ziplock bag or baking dish and pour marinade ingredients over top. Marinate in the fridge for 2-24 hours, flipping steak a few times to coat with marinade. When you're ready to make the steak, heat the grill to high heat and grill the steak for about 5 to 6 minutes, flip and grill for 4 to 5 minutes more or until your desired doneness. Let it rest for 10 minutes, then slice thin strips on an angle. You can also cook the steak under the broiler!

While the steak rests make the pesto. Combine the basil, garlic, and pine nuts in a food processor or blender and pulse until coarsely chopped. With the machine running, slowly add the olive oil and process until smooth. Add the cheese and pulse until combined. Season with salt and pepper, to taste and add the crushed red pepper if using.

Warm your pitas over and open flame on the stove for 20 seconds on both sides or in the microwave for 30 seconds. Spread a little of the pesto down the center of the pita and top with sliced steak, sliced grape tomatoes, tapenade and a drizzle more of pesto. Finish with a sprinkle of feta cheese.