Preheat oven to 180 degrees. Grease and flour a small loaf pan and set aside.
Sift together the flours, baking powder, salt and cinnamon powder in a bowl and set aside.
Beat eggs along with sugar till light and fluffy. Slowly fold in the sifted flour mixture and the oats.
Add in the oil, milk and vanilla and mix well.
Finally fold in the apples.
Bake for 50 to 60 minutes till the skewer comes out clean. If the top gets darkened, cover loosely with aluminium foil after 45 minutes and bake further.
For the topping, melt the butter, mix in the sugar and cinnamon and rigorously stir till sugar dissolves. Pour over the warm cake.
Allow to cool the cake in the pan. Slice with a knife and push out. Serve with a cup of hot tea or coffee!