Preheat your oven to 350°F (175°C).

In a mixing bowl, combine all-purpose flour, brown sugar, and unsalted butter (or coconut oil) until the mixture resembles coarse crumbs. Press this mixture into the bottom of a greased baking dish.

In another bowl, mix together the cherries, rhubarb, granulated sugar, cornstarch, vanilla extract, and cinnamon. Stir until well combined and spread the filling over the crust.

In a clean bowl, combine rolled oats, all-purpose flour, brown sugar, and melted butter (or coconut oil). Mix until crumbly and sprinkle over the filling.

Bake for 35-40 minutes until the edges are golden brown and the filling is bubbly.

Allow to cool completely at room temperature for about 1-2 hours before slicing.