Preheat the oven to 180°C.
Spread the sour cherries in a baking dish, including their liquid. If you’re using fresh fruits, then add half a cup of cherry juice to it. Add the vanilla essence, then scatter the sugar and walnuts on top and dust with cinnamon.
In a bowl, rub the butter/spread with the flour, oats, sugar & cinnamon until you get lumpy, sticky crumble. Add more butter/margarine if it feels too dry.
Cover the fruits with the crumble, slightly pressing it down with the base of a spoon.
Bake for about 20-25 minutes until golden.
Serve warm.