Preheat your oven to 350ºF (180ºC) and prepare a 9-inch round cake pan by buttering it and adding parchment paper at the bottom.

In a medium bowl, combine all-purpose flour, brown sugar, and cinnamon for the streusel topping, then mix in melted unsalted butter until crumbly. Refrigerate this mixture for 15 minutes.

In a separate bowl, whisk together all-purpose flour, baking powder, and fine salt. Set aside.

In a large mixing bowl, combine granulated sugar and lemon zest, rubbing them together until fragrant.

Using a hand mixer, beat the sugar mixture with eggs and neutral oil until light and fluffy, then add sour cream and mix until just combined.

Gradually sift in the dry ingredients, folding them gently with a spatula until just combined.

Pour the batter into the prepared pan, fold in blueberries, and sprinkle the chilled streusel topping evenly over the cake.

Bake for 40-50 minutes or until a toothpick inserted in the center comes out clean.

Cool the cake in the pan for 10 minutes before transferring it to a wire rack. Prepare the glaze by whisking powdered sugar and lemon juice, and drizzle over the cooled cake.