Mix together the garlic, chilli flakes, spices, lemon zest, juice and olive oil in a small bowl.
Place the onions and potatoes, in 2 large ovenproof dishes, pour over the spice mixture and rub in. Place in the oven and roast for 25 minutes.
Remove from the oven and add the chicken thighs and the peppers. Season with salt & pepper and put back in the oven for another 30 minutes until the chicken is cooked through. Add the cherry tomatoes for the last 10 minutes of the cooking time.
Serve in bowls with a dollop of yoghurt and a sprinkling of coriander.