Lightly grease a deep 23 cm round cake pan. Line base with paper. Lightly grease paper.
Custard: Combine custard powder and sugar in pan, gradually stir in milk until smooth.
Stir over heat until mixture boils and thickens.
Stir in butter and essence. Allow to cool.
Cake: Cream butter and sugar in a small bowl with electric mixer until light and fluffy.,
Add eggs, one at a time, beating in well between additions.
Stir in flour and custard powder.
Spread half the cake mixture into prepared pan.
Spread with custard.
Place small amounts of remaining cake mixture over custard and gently spread with small spatula.
Arrange apples over top of cake mixture and brush with melted butter.
Sprinkle with cinnamon.
Bake at 180C for approximately 1¼ hours. Cool in pan.
