Preheat the oven to 375 °F (190 °C). Line a 9 x 13 inch (23 x 33 cm) pan with parchment paper leaving excess paper extend over the top on two sides for easy removal from the pan.
In a large mixing bowl, mix flours, rolled oats, sugar, baking powder, salt and lemon zest. Transfer to a food processor. Add cubed butter and pulse 15 times. Scrape down sides and pulse another 15 times. Add the egg, pulse another 15 times and scrape down sides again. Process for another 5 to 10 seconds or until the mixture is humid and sticks together.
Transfer ¾ of the mixture to the prepared pan. Press firmly to form a crust.
In another bowl, mix haskap filling ingredients. Spread on the crust and sprinkle with reserved crumble mixture.
Bake for 45 minutes or until the crumble is golden and the haskap filling is bubbling. Let cool completely (at least 2 hours or overnight) before cutting into bars. Store in a closed container in the refrigerator.