Preheat the oven to 190°C.
Cut the onion into wedges.
Wash and pat-dry the potatoes, then cut them into bite-sized pieces if needed.
Mix the butter or spread with the cinnamon powder, salt and pepper and the leaves of 1 sprig of thyme.
Core the apple/pear, then cut it into wedges and put them in a large baking tray. Add the onion and potatoes, then scatter some thyme leaves on top.
Butterfly the chicken. Place it on a chopping board, breast-side down, then remove its backbone using sharp scissors. Turn over the chicken and flatten it by pushing down the breastbone.
Rub the chicken all over, then under the skin with the cinnamon butter. Crumble the remaining mixture over the potatoes.
Put the chicken (skin-side facing upwards) on a rack, then place this over the tray. Season with salt and pepper, then put the dish in the oven.
Bake for about 45 minutes until golden, basting the chicken with the jus a few times. If it’s getting brown too soon, cover the chicken with foil.
Test the chicken at the thighs with a skewer. If clear jus is coming out, it’s cooked through.
When the chicken is cooked, remove it to a plate together with the fruit and onion pieces, then cover and rest for 10 minutes.
Meanwhile, turn up the heat in the oven and brown the potatoes ( if you want them crispy) then transfer them to a plate and keep warm.
Transfer the cooking jus to a small pan, add some stock, wine or apple juice to make a gravy. When reduced, strain and transfer it to a small jug.
Cut the chicken into four portions and serve with the roasted fruits & onion, the gravy and side dishes of your choice.