Preheat the oven to 240°C (475°F) (220°C/425°F fan-forced).

In a large bowl, combine the beef mince, grated onion (using a box grater), garlic, cumin, ground coriander, paprika, chilli flakes (if using), salt, pepper, parsley and bicarbonate of soda. Use your hands to mix until the mixture is sticky and cohesive – about 2 minutes of firm kneading.

Line a large baking tray (or two smaller trays) with baking (parchment) paper. Press the mince mixture on the tray into a large rectangle about 1 cm (½ inch) thick – roughly 30 x 40 cm (12 x 16 inches). Keep the edges relatively tidy but don’t stress about perfection.

Use a bench scraper or metal spatula to slice the mixture vertically into long strips about 2–3 cm (¾–1¼ inches) wide, cutting all the way through to the paper. Then press shallow horizontal slits across each strip – not too deep, just enough to give that traditional kebab look and help with even browning.

Brush the top of the kebabs with olive oil. Bake on the top rack in the oven for 15–18 minutes, or until golden brown and cooked through, with crisp edges. Keep an eye on it from the 15-minute mark – depending on your oven and tray thickness, it may cook slightly faster. Optional: Grill (broil) in the oven for the final 1–2 minutes if you want deeper browning.

Make the sumac onions – While the kebabs bake, combine the finely sliced red onion, sumac, lemon juice, olive oil and salt in a bowl. Toss to coat and set aside for 5–10 minutes to pickle lightly for better flavour – or you can serve immediately.

Make the garlic yoghurt – In a separate bowl, stir together the yoghurt, garlic, lemon juice and salt. Taste and adjust the seasoning if needed.

Heat the flatbreads in a dry frying pan or directly over a gas flame for 20–30 seconds per side until soft and pliable.

Press the warm flatbreads onto the cooked meat to soak up some of the cooking juices. Separate the kebab strips along the cut lines. Serve inside or on top of the warm flatbreads with generous spoonfuls of garlic yoghurt, a pile of sumac onions, sliced tomatoes and fresh parsley.