In a large bowl, combine the Greek yoghurt, lemon juice and garlic. Add the cornflour, paprika, cumin, coriander, turmeric, cinnamon, onion powder, salt and pepper. Mix well until smooth and well combined.
Add the chicken thighs to the bowl and toss thoroughly so every piece is well coated. Cover and refrigerate for at least 2 hours if possible. Overnight is ideal, but even 30 minutes will still give great flavour.
Preheat the oven to 180°C fan-forced. Pack the marinated chicken thighs tightly into the tin, pressing them down firmly so there are no gaps.
Cover loosely with foil and bake for 40 minutes. Remove the foil and return to the oven for a further 15–25 minutes, until the top is lightly golden and the chicken is cooked through. Juices should be bubbling and clear.
Remove from the oven and rest in the tin for 10 minutes. Lift out using the baking paper, then slice thickly or thinly, pouring over any juices from the tin.
