Heat a large cooking pot on medium-low heat. Add apple and pear cubes, together with lemon juice and water. Add cinnamon stick and sugar and let everything simmer for about 15 min.
Meanwhile, roast the blanched almonds and hazelnuts in a nonstick skillet over medium-high heat until lightly golden brown. Leave to cool for a minute and then grind the nuts in the kitchen aid.
Mix all ingredients for the crumble together in a large bowl (use your hands).
Remove the cinnamon stick from the apple-pear mixture and place the latter in an oven dish. Cut the cherries in half and put them on top of the apple-pear mixture. Break up the crumble with your fingers and place on top of the fruits. Finish with the almond flakes.
Bake the crumble for about 35 min.
Serve the crumble lukewarm or cold together with plain yoghurt or some (vanilla) ice cream.