Preheat oven to 180 degrees C. Lightly grease and flour a medium glass baking dish.
In a bowl beat together margarine and 3 cups sugar until fluffy. Alternately beat in 2 cups plain flour, rice flour, baking powder and milk. Slowly beat in the eggs and Parmesan cheese. Transfer to the prepared baking dish.
In a small bowl, mix the 1/2 cup sugar, 1/4 cup (30g) plain flour and sesame seeds. Sprinkle evenly over the batter in the cake pan.
Bake 45 minutes in the preheated oven until a toothpick inserted in the centre comes out clean. Cool completely and cut into squares.