Preheat the oven to 150 degrees Celsius. Place the cut rhubarb and strawberries in your casserole dish and add the sugar and vanilla essence. Mix.
Place in the oven for 10 minutes, at 150 degrees Celsius to allow the fruits to cook.
Carefully remove the casserole dish from the oven and make a paste with a spoon of fruit juices from the bottom of the dish, and the cornstarch. Mix the cornstarch paste into the fruit. Add the lemon zest.
Place the dish back into the oven for another 10 minutes, until the fruit is juicy, roasted and slightly thickened.
Combine the crumble ingredients in a mixing bowl – the oats, flours, almonds, sugar, spices and coconut oil. Mix well until combined.
Top generous helpings of crumble topping over the roasted fruits, and bake for another 15 minutes, until the crumble is dark, crunchy and toasty.
Grab a spoon and share with your favourite person.