Put the butter in a bowl and mix at high speed for 2 minutes until it is creamy.
Add the cream cheese and mix for another 2 minutes.
Add the sugar and mix at high speed for 1 minute.
Add the sour cream and vanilla and mix everything together at high speed for about 1 minute.
Now set the mixer low and add the eggs 1 by 1. Only add the next egg when the previous one is incorporated.
In a second bowl, mix together the flour, cornflour, baking powder and salt with a whisk and add to the batter. Mix at a low speed until everything is well mixed, but immediately stop mixing because otherwise you will knock the air out and you get a dense cake.
Pour the batter into the cake tin and put in the oven. Bake for 90 minutes.
Check if the cake is cooked by sticking a satay stick in the middle. If it comes out dry, the cake is done.
Let stand for 5 minutes and then remove the cake from the tin. Allow to cool on a rack.