Prepare the crumble by mixing all crumble ingredients in a bowl. Chill in the refrigerator.
Preheat oven to 350°F (175°C). Grease and line a loaf pan.
Rub lemon zest into sugar to release flavor.
Mix in flour, baking powder, and salt.
Add butter gradually while mixing until crumbly.
Mix in vanilla, then eggs one at a time.
Add lemon juice and milk. Mix until smooth.
Toss blueberries with flour and gently fold into batter.
Pour batter into pan, top with extra berries and crumble.
Bake for 50–60 minutes until a toothpick comes out clean.
Cool for 45 minutes.
Whisk icing ingredients and drizzle over the cooled Lemon Blueberry Loaf.