1. 1. Prepare the Doner Meat Mixture: In a large mixing bowl, combine the ground lamb or beef with the grated onion, minced garlic, ground cumin, smoked paprika, dried oregano, salt, and black pepper.

2. 2. Mix Thoroughly: Using your hands, mix all the ingredients together vigorously. Knead the mixture for about 5-7 minutes. This is crucial for developing the proper texture.

3. 3. Shape the Meat: On a baking sheet lined with parchment paper, form the meat mixture into a compact, log-like shape. Press it firmly.

4. 4. Bake the Meat: Preheat oven to 375°F (190°C). Bake for 45-60 minutes, or until cooked through (internal temp 160°F/71°C) and browned.

5. 5. Rest and Chill: Cool completely, wrap tightly in plastic wrap, and refrigerate for at least 2-3 hours or overnight.

6. 6. Prepare the Garlic Yogurt Sauce: Whisk together Greek yogurt, minced garlic, lemon juice, and dill/parsley (if using). Season with salt and pepper. Refrigerate.

7. 7. Slice the Meat: Unwrap the chilled meat log. Using a very sharp knife, slice as thinly as possible.

8. 8. Sear the Slices: Heat a large skillet over medium-high heat with olive oil. Sear slices in a single layer for 2-3 minutes per side until crispy. Work in batches.

9. 9. Warm the Pitas: Lightly toast or warm pita breads until soft.

10. 10. Assemble Your Kebabs: Open each pita, fill with meat, shredded lettuce, sliced tomatoes, onions, cucumber, and garlic yogurt sauce. Serve immediately.