Marinade:
2 large onions, chopped
2 garlic cloves, crushed
½ cup olive oil
2 tablespoons lemon juice
1 teaspoon dried oregano
1 teaspoon ground black pepper
½ teaspoon ground turmeric
1 pinch curry powder
1 teaspoon salt, plus more to taste
1 pound beef flank steak, thinly sliced
Tzatziki Sauce:
8 ounces sour cream
2 tablespoons olive oil
1 tablespoon lemon juice
½ teaspoon salt
½ teaspoon ground black pepper
1 tablespoon chopped fresh dill
1 clove garlic, crushed
6 pita bread rounds
Make marinade: Place onions in a large ceramic bowl and crush with the bottom of a glass until juice is rendered and onions look translucent. Stir in garlic, olive oil, lemon juice, oregano, black pepper, turmeric, curry powder, and salt. Add beef and toss to coat. Cover the bowl with plastic wrap and marinate in the refrigerator, 8 hours to overnight.
Make sauce: Combine sour cream, olive oil, lemon juice, salt, black pepper, dill, and garlic in a medium bowl; mix until well combined. Cover the bowl with plastic wrap and refrigerate for 8 hours to overnight.
Preheat the oven's broiler and set the oven rack about 6 inches from the heat source.
Remove meat from marinade, brushing off extra onions; discard marinade. Spread meat on a baking sheet without overlapping. Season with salt.
Cook under the preheated broiler until meat is browned and crispy, about 3 minutes per side, turning halfway through cooking.
Divide meat between pita breads and drizzle with tzatziki sauce to serve.
