1. Preheat the oven to 170°C/340°F.
2. In a large bowl, beat the softened butter with the icing sugar and vanilla until light and fluffy. Add the egg yolks and beat again.
3. Combine the butter base with the cream cheese and beat until combined.
4. In another bowl, combine the flour, baking powder and cornflour.
5. Beat the egg whites with the lemon juice separately until stiff.
6. Combine the dry ingredients with the butter and cream cheese mixture. Add the whipped egg whites.
7. Pour the mixture into a 16cm baking tin and bake for 40 minutes.
8. Let the cheesecake cool completely before cutting.