Melted butter, to grease
450g (3 cups) self-raising flour
150g (1 cup) plain flour
440g (2 cups) caster sugar
300g butter, cubed, at room temperature
310ml (1 1/4 cups) milk
6 eggs, at room temperature
3 tsp vanilla essence
Preheat oven to 140°C. Position a rack on the second lowest shelf of the oven. Brush a round 25cm (base measurement) cake pan with the melted butter to lightly grease. Line base and sides with non-stick baking paper.
Place the self-raising flour, plain flour, sugar, butter, milk, eggs and vanilla essence in a large mixing bowl. Use an electric beater to beat on low speed for 30 seconds or until just combined. Increase the speed to high and beat for 1-2 minutes or until the mixture is thick and all the butter is incorporated. Spoon the mixture into the prepared pan and smooth the surface with the back of a spoon.
Bake in preheated oven for 2 1/2 hours or until a skewer inserted into the center of the cake comes out clean. Remove from oven and set aside for 10 minutes. Turn onto a wire rack for 2 hours or until completely cool.
Serve with a dusting of confectioner's sugar or a dollop of whipped cream.
Note: This vanilla butter cake's richness and moistness is best enjoyed at room temperature. It tends to stiffen, dry out, and lose flavor when refrigerated, so avoid filling or frosting in advance with ingredients that must be refrigerated, such as cream cheese frosting and pastry cream.