Preheat your oven to 160 degrees Celsius.
Prepare the apples: peel, slice around the core and dice the apple into small pieces. Place into a bowl, add in the flour, lemon juice and zest, cinnamon, salt and sugar and stir to combine.
Prepare the crumble: melt the butter in the microwave, add in the flour, salt, brown sugar, and cinnamon and stir to combine. The crumble mixture should resemble wet sand.
Place the apples into an oven safe dish and spread evenly across the bottom of the dish. Sprinkle the crumble evenly across the top of the apples.
Bake in the oven for 30-45 minutes or until the top of the crumble is a slightly deep golden.
Remove from the oven, allow to cool for 15-20 minutes before scooping into a bowl and serve with custard or ice cream. Note 4