¾ pound portobello mushroom caps, sliced 1/2-inch thick
1 medium red onion, halved and cut into 1/3-inch wedges
3 tablespoons plus 2 teaspoons extra-virgin olive oil
1 teaspoon ground cumin
¾ teaspoon ground coriander
½ teaspoon ground sweet or smoked paprika (optional)
Kosher salt and black pepper
2 packed cups very thinly sliced red cabbage (about 6 ounces)
¾ cup low-fat or whole-milk Greek yogurt
¾ teaspoon ground turmeric
Cilantro or mint, for serving
Heat the oven to 425 degrees. On a large rimmed sheet pan, drizzle the mushrooms and red onion with 3 tablespoons oil. Sprinkle with cumin, coriander, paprika (if using), 1 teaspoon salt and 1/2 teaspoon pepper; toss to coat. Arrange in an even layer and roast until tender and browned, about 20 minutes. Add the pitas directly to the oven rack to warm during the last 5 minutes of cooking.
Meanwhile, toss cabbage with remaining 2 teaspoons oil in a medium bowl; toss to coat. Season generously with salt and pepper. In a small bowl, stir together yogurt and turmeric; season with salt and pepper.
To serve, slather yogurt over warm pitas. Top with cabbage, mushroom mixture and herbs, and serve immediately.