Preheat oven to 350°F (180°C). Spray an 8-inch square baking pan with cooking spray and line with parchment paper. This will help with easy removal.
In a medium saucepan, combine the cut rhubarb, raspberries, apple, sugar and water together and bring to a boil. Lower the heat and cook for about 15 to 20 minutes, covered stirring from time to time until the fruit is tender and compote is thickened. Remove from heat and allow to cool.
In a separate bowl stir Rogers Foods Original Porridge Oats & Healthy Grains, butter, brown sugar, cinnamon and coconut together into a crumbly mix. Set aside.
In the bowl of a stand mixer, place sugar, butter, egg and vanilla and beat with the paddle attachment for 3 minutes, until creamy. Add the Greek yogurt and mix until blended. Finally add Rogers Foods No Additive All Purpose Flour, baking powder and salt into wet mixture and mix until the batter is just moistened. The mixture is quite thick.
Pour cake mixture into the prepared baking pan and spread with a spatula. Spoon the cooled compote over cake mixture into about ½ inch thick layer. Sprinkle the crumble mixture evenly over the compote layer. Bake on the middle rack for 40 minutes, until the top is golden and a skewer comes out clean.Remove from oven and allow to cool completely before removing from the pan. Once cooled, remove and cut into 16 squares. Enjoy as is or serve with a dollop of Greek yogurt or a scoop of vanilla ice cream.