Preheat the oven to 170 C (150 Fan)/325F/ Gas Mark 3
For the crumble topping- you could sift the 100 grams flour and ½ tsp baking powder into a bowl and then rub in the 75 grams butter with your fingers until breadcrumbs like before mixing in the 75 grams sugar. I just blitz the lot in my food processor until sandy and rubbly - just keep whizzing. Place in the fridge to chill until you're ready for it.
For the cake-cream 100 grams butter until soft in a free standing mixer or with a hand held whisk. Add 100 grams sugar and whisk until pale and fluffy .Beat in the 2 eggs one at a time before sifting the 1½tsp cinnamon, 175 grams flour and 1 heaped tsp baking powder into the bowl. Whisk until mixed through then add 3 tbsps milk and whisk again. You may need to add more milk to get it to a soft dropping consistency.
I use an 8 inch loose bottomed square cake tin. It is a deep one though. A 9 " would be the better bet if your tin is not as deep. Fill the tin with the cake batter as levelly as you can. Spread the apple mixture gently over the cake batter. Scatter the crumble mix all over and bake the cake for 45/50 minutes. Watch carefully at the end as the top can start to catch.
Leave to cool in the tin before gently running a knife around the edge and removing. I cut mine into 2.5 inch squares for 9 large portions.
If making the stewed apples from scratch you would need 500 grams of bramley apples, 4 tbsps water and about 50-90 grams of sugar depending on how tart your apples are. Simmer gently until soft and broken down. Allow to cool a little before putting on top of the cake batter.
Store in an air tight container
It is best eaten on the same day as it is baked if serving cold. The crumble loses it's crispness if stored for longer. If you are reheating it then this doesn't matter.
I reheat in the microwave in 20 second blasts until piping hot.