Rub together the sugar, flour and butter until the mixture resembles breadcrumbs, leave to the side for now.
Preheat your oven to 180C/160C Fan and line a 9x13" traybake tin.
Peel and core the apples, cube the apples into about 2cm pieces.
Put the apples into a bowl, and cover with 50g of light brown sugar. Mix it up so all the apple pieces are covered and leave to the side.
Beat together the butter and sugar until light and fluffy.
Add in the flour, eggs, vanilla and cinnamon and beat until smooth. Fold through the apple mixture and pour the mixture into the tin!
Sprinkle the crumble mixture onto the cake!
Bake in the oven for 50-60 minutes or until baked through (Can take a little less, or a little more than an hour - depends on your oven, see tips below)
Leave the cake to cool in the tins for 10-15 minutes and then transfer to a rack to cool completely.
Once the cake has cooled - stir together the icing sugar and cinnamon, and then as much water as you like - I like it thick and drizzly!
