For the crumble, mix the flour, sugar and salt.
Add butter in pieces and work into crumbles.
Grease a large casserole dish (or several small ones) with butter.
Peel and core the apples and pears and cut into small pieces. (about 1 cm)
Peaches and plums do not need to be peeled, also cut into pieces.
Mix all the fruits with sugar and cinnamon.
Pour into the baking dish.
Add the crumble on top.
Bake in the preheated oven at 180° C for about 40-45 minutes.
The crumble tastes lukewarm or cold.