Preheat the oven to 200°C.
Over low-medium heat, pour and heat the caster sugar in a small hob-proof baking dish/casserole, stirring for about 5 minutes until it caramelizes.
Mix together the cinnamon, vanilla seeds and grated apples and pour it in, cooking the mixture for 1–2 minutes.
Mix in the apple chunks and the cranberries, then the lemon zest and juice until combined.
Take off the heat and set aside.
In a separate bowl, place the flour, sugar, butter and cinnamon, rubbing together with your fingertips until the mixture is similar to breadcrumbs.
Add the granola and blend until completely combined.
Sprinkle the crumbled topping over the first mixture prepared and re-heat the dish on the hob until simmering.
Once the apple mixture has simmered, move it to the oven and bake for 13 minutes or until the top layer is a nice golden colour.
Remove and serve warm.