Preheat oven to 180 degrees C. Grease a 20x30cm baking dish.
Place the plums into the bottom of the prepared baking dish. In a large bowl, mash together 170g butter with 1 1/2 cup of white sugar until the mixture is smooth and creamy. Beat in eggs one at a time. Stir in 3 cups of flour, the baking powder and salt. Mix in the milk and vanilla essence to make a smooth batter. Pour the batter over the plums.
Mix 1 cup of sugar, 125g of butter, 1/4 cup of flour and cinnamon together in a bowl to make a crumbly topping; spread over the batter.
Bake in the preheated oven until a toothpick inserted in the centre of the cake comes out clean, 45 to 50 minutes.
First of all, I have to say that this is a delicious recipe! An excellent way of using seasonal fruit and the desert is huge so I highly recommend if you have a lot of mouths to feed (ie. morning tea at work?). The baking time for me was much longer than recommended. This could be my oven, or my baking dish, but I found an extra 30 minutes was required. The cake portion is quite dense so small pieces are fine to serve. The plums were delicious and tart and left me wanting more! Thank you for this recipe and I will definitely use again!! - 27 Feb 2016