Separate egg whites from yolks.

Whisk whites using a hand beater on low-medium speed until stiff.

Add egg yolks and continue beating for another five minutes.

Add sugar gradually to egg mixture while continuing to beat on low-medium speed.

Sift flour, cream of tartar and cornflour three times.

Fold dry ingredients through egg and sugar mixture using a spatula.

Combine melted butter, boiling water and bicarb soda. Once combined, add to mixture and combine well using a spatula.

Pour mixture into a lined round cake tin and bake in a moderately slow oven for 50 mins.

Once cake is cooked, allow to cool for two minutes before turning out onto a cooling tray covered with two clean tea towels.

To make condensed milk filling, pour condensed milk into a bowl.

Juice the two lemons and add the lemon juice to the condensed milk.

Whisk by hand until mixture is an even, thick consistency.