Preheat your oven to 180 °C. Grease and line an 8 inch round pan with grease-proof paper on the bottom and sides of the pan.

In a medium bowl, measure and sift the flour and cinnamon. Sift the dry ingredients again into another medium bowl; then set aside. (Sift three or more times.)

Measure your caster sugar and place it into a small bowl, set aside.

Separate your eggs; pouring the egg whites into a large mixing bowl and the yolks into a smaller bowl.

Using an electric mixer on medium speed; beat the egg whites until they form soft white peaks. This should take about 2 to 3 minutes.

Gradually add your caster sugar onto the egg whites mixture a table spoon at a time; beating after each addition to incorporate the sugar. (This also ensures that you will maintain the volume of the egg whites) Add the vanilla and beat for about half a minute to incorporate.This step will take about 2 to 3 minutes.

Now add your egg yolks, one at a time, in order to maintain the volume. Beat each egg yolk into the egg white mixture thoroughly after each addition. This should take about 2 minutes and your mixture will be a nice pale yellow.

Using a spatula ; sift and fold in your dry ingredients into the egg & sugar mixture three separate times. Make sure you sift and fold very gently each time. At the same time, you don’t want to take too long folding; your sponge cake batter might collapse. Ensure you have incorporated the flour and cinnamon thoroughly.

Pour the batter into your prepared baking pan and place it in your oven; preferably in the middle rack.
Bake the cake for about 20 to 25 minutes. You can also check it with a skewer or cake tester to make sure it is baked.

Remove sponge cake from oven and leave to cool in pan for about 5 minutes. You can then remove the sponge from pan, peel off the grease-proof paper and set on a cooling rack to cool completely. This should take no longer than an hour.