Preheat oven to 220 degrees C. Grease and flour a 23cm square pan.
In a large bowl mix together the flour, baking powder, sugar and salt. Cut in the shortening with a pastry blender to the size of small peas.
In a separate small bowl, beat the egg well then stir in the milk and vanilla. Add the egg-milk mixture to the flour mixture all at once. Stir carefully until just blended.
Pour batter into prepared pan and spread evenly. Drizzle top with melted butter.
In a small bowl mix together brown sugar, 2 tablespoons flour and 1/2 teaspoon cinnamon. Sprinkle on top of cake. Pour batter into prepared pan. Bake in the preheated oven for 15 to 20 minutes, or until a toothpick inserted into the centre of the cake comes out clean.