Preheat the oven to 350℉
Make the topping: Mix into the bowl with the topping ingredients. Transfer the mixture back to the food processor and pulse to combine, do not over-pulse! Set aside.
Make the filling: In a medium bowl, mix together the rhubarb, strawberries, sugar, flour, lemon juice, vanilla, and salt.
Prepare your baking tray: Pour in the mixture and top with the crumb topping. Grab fistfuls of topping to make big chunks that hold together - this is the best part, when it cooks you get big chunks of crumble.
Top the filling with the crumb topping. Grab fistfuls of topping to make big chunks that hold together - this is the best part, when it cooks you get big chunks of crumble.
Bake for 65 minutes, or until the fruit bubbles, the topping browns, and the crust is lightly golden but not overly brown! Check at the 55-minute mark - the baking time will differ based on your oven setting.