Preheat your oven to 350*F and place a rack in the center of the oven. Grease & line an 8"x4" loaf pan with parchment. Place the loaf pan on a sheet tray.

To prepare the crumb- Combine all of the crumb topping ingredients in a medium bowl and work with your fingers until crumbly and uniformly combined. Set aside.

To prepare the cake- Whisk together in a bowl the flour, baking powder and salt. In a separate bowl combine 1 Tablespoon of the dry ingredients & the blueberries and then gently toss together, set aside.

In the bowl of your stand mixer combine the granulated sugar, brown sugar, and lemon zest and use your hand to rub the zest and sugar together until the mixture is fragrant. Add the softened butter, oil and vanilla. Mix on low to combine and then beat on medium speed for 3 minutes or until smooth and fluffy.

Scrape the bowl and beater then add the egg and mix on medium speed until combined.

Add half of the flour mixture and mix on low to combine. Add the buttermilk and mix on low to combine, then add the remaining flour and mix until almost all of the dry ingredients are incorporated. Gently fold in the flour coated blueberries.

Spoon the batter into the prepared pan and top with the crumble, breaking up large pieces of crumble if needed.

Bake for 50-55 minutes or until a toothpick inserted in the center comes out with a few moist crumbs. Allow to cool in the pan for 25 minutes then remove the loaf from the pan and transfer to a cooling rack to cool completely.

To glaze the cake combine the confectioners sugar, lemon juice and salt in a small bowl and stir together with a fork until smooth. Drizzle the glaze over the cooled cake.