1. Roast tomatoes: Preheat oven to 325°F. Line a baking sheet with parchment. Lay tomatoes cut-side up on sheet; drizzle with oil. Sprinkle with salt and pepper. Roast until tomatoes have collapsed, 30 to 40 minutes. Let cool.
2. Make pesto: In a mini food processor, pulse garlic, pistachios, basil and salt until finely chopped. Add oil a bit at a time, processing in bursts, until pesto is emulsified.
3. Make tapenade: In a mini food processor, pulse olives, capers and anchovy paste, if desired, until pastelike. Drizzle in a touch of oil, if desired. Season with a squeeze of lemon juice.
4. Serve: Spread labneh in a shallow bowl. Using back of a large spoon, make a wide indentation in the center. Dollop with roasted tomatoes, pesto and tapenade. Serve with pita.