Slice the meat into very thin slices, about 4-5 cm/ 1.5-2 inches long, and place them in a large, non-reactive bowl.
Marinate: Add all the spices. Grate the garlic cloves and slice the onion into thin half-rings. Add them to the meat together with the lemon juice and olive oil. Do not add any salt at this stage, salt the meat after cooking it. Mix well and place the bowl in the fridge. Leave the meat to marinate for at least 1 hour, but preferably for several hours.
Tzatziki:
Roughly grate the cucumber (large side of the box grater). Place in a colander, sprinkle with a tablespoon of salt and leave to drain for about 30 minutes. Place in a clean kitchen towel and squeeze as much water out of it as you can.Mix the cucumber, yogurt, lemon juice, grated garlic cloves and finely chopped dill in a bowl. Adjust the taste with salt and pepper.
Cook:
Preheat the oven to 200 degrees Celsius/ 400 degrees Fahrenheit.
Cook meat: Heat a large cast-iron skillet or non-stick pan and cook the meat on high heat until browned and cooked through, about 2-3 minutes, but check. Salt the meat to taste. Don't overcrowd the pan, if it is too small, it is preferable to fry the meat in two batches.
Heat bread: In the meantime, place the flatbread in the hot oven and heat for about 2-3 minutes until heated through and lightly crisp on top. Take it out and quarter it. Cut each piece horizontally (don't cut through) to obtain a pocket.
Cabbage: Finely slice the red cabbage and place it in a bowl. Add some salt and knead the cabbage for a minute or so to soften it. Add the olive oil, some pepper, and more salt, if necessary. Mix well.
Serve:
Slice the onions and tomatoes.Smear the inside of the bread with some tzatziki, add some onion and tomato slices, some shredded red cabbage, and the meat. Serve with more tzatziki and vegetables on the side.
Video
Notes
Boneless, skinless chicken thighs or pork neck are also great. It's a German-style doner, so pork it's allowed.