turn on the oven to 225c.
melt the butter in a pot, in the meanwhile, cut the apples into 2cm cubes.
then mix the butter, sugar and oats together.
place the apples into a lightly buttered baking dish and sprinkle some cinnamon on top.
add the crumb mixture on top.
bake until the apples are soft and the crumb has a nice brown color, it should take about half an hour.
enjoy with vanilla sauce or ice cream.