Preheat the oven to 180°C, fan 160°C, gas mark 4. Lightly grease a 20cm round non-stick cake tin.
In a large mixing bowl, cream the butter and sugar together until pale and fluffy. Slowly add the eggs, beating all the time.
Gradually fold in the flour, baking powder, cinnamon, mace and milk, then pour the mixture into the prepared cake tin.
Bake for 40 minutes until the sides just begin to come away from the tin. Mix together a teaspoon of the extra sugar and ½ teaspoon of the cinnamon, then sprinkle over the cake and return to the oven for 5 minutes to glaze.
Carefully remove the cake from the tin and cool on a wire rack.