Pit the cherries and transfer to a large bowl. Toss with the sugar and kirsch and set aside.

Melt the butter in a small sauce pan. In a large bowl, combine the flour, oats, sugar, and salt and stir to combine. Pour the butter and use your hands to incorporate until a crumbly, dry dough forms. Set aside.

Lightly coat a 13''x10'' baking pan (At least 2'' deep) with baking spray. First, pour in half the crumble mixture and use your fingers to press it into a the bottom of the pan in a firm, even layer. Next, add the cherries in over top and spread it into an even layer. Finally, top with the remaining crumble mixture on top in an even layer. Transfer to the oven and bake for 30-40 minutes until the top is golden brown and the cherry filling is bubbling.

Divide the crumble between dessert plates and serve warm with vanilla ice cream, if desired. Store leftovers in the fridge. Enjoy!