Preheat your oven to 200°C (400°F).

In a large bowl or food processor, combine grated onion, minced garlic, ground beef, paprika, oregano, salt, and black pepper. Mix until tacky, about 2-3 minutes.

Place the meat mixture between two sheets of parchment paper and press into a thin rectangle. Roll it tightly into a log shape and twist the edges to seal.

Bake the wrapped kebab log on a lined baking tray alongside halved tomatoes and long green peppers for 30 minutes until cooked through.

Once baked, unwrap the parchment paper, let rest for a few minutes, then slice into strips.

Spread kebab pieces evenly on the tray, set the oven to broil and broil for 3-5 minutes until crispy.

Whisk together mayonnaise, sour cream, minced garlic, black pepper, salt, and water for the garlic sauce. In another bowl, combine sliced red onions with sumac, parsley, olive oil, lemon juice, and salt to marinate.

Serve in warm flatbreads or salads, layering kebab pieces, drizzle with garlic sauce, and top with marinated onions.