For the Strawberry Rhubarb Filling: Position a rack in the middle of the oven. Preheat the oven to 375°F/190°C. Coat a 9-inch (23 cm) ovenproof glass or ceramic pie plate with nonstick spray; set aside.

For the Crisp Topping: Melt the butter in a medium-size microwave-safe mixing bowl in the microwave on low. (Or melt the butter in a small saucepan on your stove top, if you like, then transfer to a medium-size mixing bowl.) Whisk in the brown sugar, then whisk in the flour, oats, cinnamon, and salt until well combined. Use your hands to help form clumps then scatter them evenly over the strawberry rhubarb filling.

Bake for about 35 to 45 minutes, or until the topping is golden and the fruit is bubbling around the edges. Let sit for 5 minutes before serving, to allow the juices to thicken. The crisp may be served at room temperature, or rewarmed after cooling. I think the textures of the crisp are best the day it is baked. It will hold overnight but the “crisp” will soften and some of the juiciness of the fruit filling with absorb into the topping. If you must hold the crisp, lightly cover with aluminum foil and store at cool room temperature.