Separate the egg yolks and egg whites into two bowls. Place the egg whites in the fridge to chill.
To the egg yolks, add the flour, milk of choice, corn starch (saving some for egg whites), baking powder, vanilla bean paste and sweetener. Mix thoroughly until the batter is smooth and free of lumps.
Remove the chilled egg whites from the fridge. Add the remaining corn starch and beat with an electric mixer until stiff peaks form. You’ll know they’re ready when you lift the beaters and the peaks hold their shape without drooping.
Gently fold 1/3 of the whipped egg whites into the egg yolk batter to loosen it. Then pour this mixture back into the remaining egg whites and carefully fold until just combined, being careful not to deflate the mixture.
Pour the batter into an ungreased 8-inch cake tin (avoid non-stick tins, as the cake needs to cling to the sides to rise properly).Bake at 155°C for 50 minutes.
Once baked, immediately invert the cake tin and allow the cake to cool completely upside down. Let the cake cool completely.