- Dice the rhubarb and the peeled and cored apple.
- Place the diced fruits in a buttered baking dish, then sprinkle with vanilla sugar.
- Make the crumble by rubbing the flour and the butter together with your fingers then add sugar.
- Sprinkle the crumble evenly over the fruits.
- Heat the oven at 210°C.
- Bake for 25 to 30 minutes until golden brown on top.