• Preheat oven to 350℉. Coat an 8-inch square baking dish with baking spray.

Prepare the Fruit

• Using a sharp knife and cutting board, slice 2 cups fresh or frozen rhubarb and 1 cup fresh or frozen strawberries.
If you are using frozen rhubarb and strawberries, you may either thaw in the refrigerator overnight or defrost in the microwave. I used frozen strawberries and placed them in a glass bowl to defrost. After that, I coarsely mashed them with a potato masher.
• Peel and dice 1 large honey crisp apple.

Make the Filling

• In a medium bowl, combine the sliced rhubarb, strawberries, and diced apples. Sprinkle with 1/3 cup granulated sugar and 3/4 teaspoon ground cinnamon. Mix to combine.
• Spoon the strawberry filling into the prepared baking dish.

Prepare the Crumb Topping

• In a small bowl, combine 1/2 cup all-purpose flour, 1 teaspoon baking powder, and 1/4 teaspoon salt.
• Using a pastry fork, cut in 3 tablespoons butter (cold) until it resembles coarse crumbs. Mix in 2/3 cup brown sugar and 1/2 cup old-fashioned oats to combine.
• Sprinkle the oat mixture over the strawberry filling. Gently press the crumb into the filling with a wooden spoon. (This helps the filling to bubble up to the top.)
• Bake in preheated oven until golden brown and bubbly, approximately 45-50 minutes. Allow to cool for 5-7 minutes before serving.
• Serve warm with whipped cream or vanilla ice-cream. This recipe serves 4-6.