Preheat the oven to 350°F (180°C) and prepare a 9×5-inch (23×13 cm) loaf pan by greasing and flouring it or by spraying it with cooking spray and covering it with parchment paper.
In a large mixing bowl, whisk the all-purpose flour, baking powder, and salt and set aside.
In a separate bowl, rub the sugar with the lemon zest using your fingers to release the oil from the lemon zest. This will intensify the lemon flavor in the cake.
With the mixer running on medium-low speed, cream the butter. Then add the sugar and lemon zest mixture and mix until well combined.
Incorporate the eggs, one at a time, while you continue mixing.
Add the milk, lemon juice, and vanilla extract.
Add the dry ingredients to the batter and mix to incorporate. Scrape the sides and bottom of the bowl with a spatula to make sure everything is well blended.
Toss the blueberries with a few tablespoons of all-purpose flour and then fold in 1 cup (100 g) of the blueberries into the batter.
Pour the batter into the prepared loaf pan. Top with the remaining ½ (50 g) cup of blueberries, followed by a layer of the chilled crumble.
Bake for 55 minutes to 1 hour or until a toothpick or skewer inserted in the center comes out clean.
Let the loaf cool on a wire rack before drizzling it with the lemon icing.