In a large bowl, combine the ground lamb, ground beef, and chopped lamb meat, finely chopped onions, green peppers, tomatoes, minced garlic, chopped parsley, cumin, paprika, chili flakes, salt, and pepper. Mix thoroughly until all ingredients are well incorporated.
Preheat the oven to 180°C (356°F).
Spread the meat mixture onto a round baking tray, pressing it down to form a uniform layer with a thickness of 1 cm (0.4"). f your tray is too big, you can leave the sides empty and fill the gap with thinly sliced potatoes, slightly overlapping them.
Top the meat mixture with tomato wedges and sliced peppers.
In a small bowl, mix the tomato paste, red pepper paste, and olive oil with water to create a sauce. Skip the olive oil if your meat mixture has a high fat percentage.
Pour this sauce evenly over the meat and potatoes.
Bake the kebab in a hot oven for about 40 -45 minutes, or until the potatoes are tender and slightly golden and the meat is cooked through.