Preheat the oven to 375 degrees Fahrenheit and grease a 13×9-inch baking pan. In a mixing bowl, combine the blueberries, 1/4 cup sugar, and lemon juice. Stir until well mixed and set aside.

In a separate bowl, mix together the 3/4 cup white sugar, brown sugar, baking powder, ground almonds, cake meal, salt, and lemon zest until well combined. Add the butter and the egg and use a pastry cutter to blend the ingredients until well combined and you still have pea-sized chunks of butter. Add the almonds and mix them in.

Place half of the crust mixture into the baking dish and press it firmly into the bottom. Spoon the blueberries overtop, careful not to add too much of the liquid. Crumble the rest of the crust mixture overtop the blueberries so that it is evenly distributed. Bake for 50 minutes until the crumb topping is golden brown.

Let cool for at least an hour before cutting, so they set. Cut into 24 squares. They are best served just slightly above room temperature, but store any leftovers in the refrigerator.