Preheat the oven to 375 degrees. Prepare a 9x13 baking pan with butter or cooking spray, and line with parchment if desired for easy removal.
Whisk together the flour, sugar and baking powder in a large bowl.
Cut the butter in small chunks and add to flour mixture. Using a pastry blender or your hands, work the mixture until crumbs are formed.
Add the egg and work into the mixture until fully combined.
Press about 3 cups of the mixture into the bottom of the prepared pan firmly. Set aside the remaining crumb mixture for the topping.
In a large bowl, combine the cranberries, sugar and cornstarch. Mix well.
Pour the cranberries over the crust, ensuring that leftover sugar from the bowl is also poured on top.
Using a spoon, sprinkle the remaining crumb mixture on top of the cranberries.
Bake for 50 minutes or until the top is slightly golden.
Cool to room temperature. You can serve at room temperature or put it in the refrigerator until slightly chilled.