Preheat the oven to 180°C (gas mark 4, 350°F) and line a baking tray with parchment paper.
Cream the butter and sugar in a large mixing bowl until the mixture is light and fluffy.
Add the egg and vanilla into the mixing bowl and mix together.
Pour the plain flour, baking powder, salt and cinnamon into the mixing bowl and mix together until a dough is formed.
With a spoon, scoop a walnut size of dough and place it into the palm of your hand. Roll the dough into a ball and coat it in the cinnamon and sugar mixture. Then place on a lined baking tray.
Bake the cookies in the oven for 12 to 15 minutes and leave to cool for 5 minutes once baked.